Borderlands 2 pop culture references

DC Comics
Blackest Night Siren skin is a reference to the Green Lantern's oath, and DC Comic's cross-over event, Blackest Night.

Zer0 has a skin called "Blue Scarab" a reference to the DC character Blue Beetle, a blue-scarab-themed character whose powers were derived from advanced alien technology.

Hamlet
Occasionally, a Psycho will say "Oh, that this too too solid flesh would melt, thaw and resolve itself into a dew!" This is a reference to William Shakespeare's Hamlet. -Actually, he launches into the entire 'Too Solid Flesh' solilouqy from Hamlet, timing about two and half minutes worth of Shakespearian screaming.

Upon dying, Goliaths may say "Goodnight, sweet prince.", which is a quote from Hamlet and also a popular term on the internet used when a celebrity or any other notable individual has died.

The Hyperion New-U station has a chance to, upon respawning, say: "Welcome back from your visit to the undiscovered country!" A reference to the extremely well known "To be, or not to be" soliloquy from William Shakespeare's "Hamlet".

The Hitchhiker's Guide to the Galaxy
Sometimes, when an enemy's weak spot is highlighted with B0re, the text near the highlighted area says 42, which is "The Answer to the Ultimate Question of Life, the Universe, and Everything" in "The Hitchhiker's Guide to the Galaxy" franchise.

In addittion, the action skills of Axton and Salvador have a base cooldown of 42 seconds.

In the second Lost ECHO recording detailing Zer0's backstory, Handsome Jack tells Angel: "Angel, you've got a brain the size of a planet. Don't give me 'I dunno,'" a reference to Marvin the Paranoid Android's "brain the size of a planet" lament.

At the beginning of the game, Claptrap says that the programmers gave him an upbeat personality since his actual personality is quite depressed. This maybe a reference to Marvin the Paranoid Android's depressed personality.

The Ice Man Cometh
The Quest "The Ice Man Cometh" is a reference to a play of the same name, written by Eugene O'Neill in 1939. This could also be a reference to one of Mr. Freeze's (Arnold Schwarzenegger) quotes from Batman and Robin.

The Lord of the Rings
The ECHO recording from the beginning of the quest "The Bane" sounds oddly familiar to the way Gollum says "Shire... Baggins..." while being tortured in the book by J. R. R. Tolkien: "The Lord of the Rings: The Fellowship of the Ring." The quest itself, including the gun, could be a reference to the "Lord of the Rings" trilogy, with the way the gun speaks when you use it.

There's another reference in Eridian Blight, the player must bring the item "Geary's Unbreakable Gear" to Geary on top of the volcano. For more information visit the character page.

Macbeth
The mission "Toil and Trouble" is a reference to the line spoken by witches in William Shakespeare's Macbeth.

The Man With the Golden Gun
There is a skin called "The Man With the Golden Pun". This is a reference to the twelfth James Bond novel, and the ninth James Bond film, "The Man With the Golden Gun".

No Country for Old Men
Sometimes in Sanctuary a random Crimson Raider will say, "This is no planet for old men.", referencing the novel and movie No Country for Old Men.

The Once and Future King
The quest "The Once and Future Slab" is a reference to the Arthurian fantasy novel The Once and Future King written by T. H. White in 1958.

Paradise Lost
One of Axton's skins, "Red Right Hand" is a reference to Nick Cave & The Bad Seeds's song "Red Right Hand", as well as--along with the song--a reference to John Milton's Paradise Lost.

It may also (Though very unlikely) be a reference to the Character of Nefarian serpine, from the Skulduggery Pleasant book series, Written by Derek landy.

Portrait of the Artist as a Young Man
The challenge "Portrait of the gunzerker as a young man" may be a reference to the film title.

Romeo and Juliet
A weapon, given by Moxxi, has red text that reads "A Rose by another name" which is a reference to the line "A rose by any other name would smell as sweet." in William Shakespeare's Romeo and Juliet.

Slaughterhouse 5
Sometimes when Maya kills an enemy, she will say "So it goes.", a phrase used in the novel whenever the protagonist is confronted with death.

A Song of Ice and Fire Series
Occasionally, a Crimson Raider in Sanctuary will say, "Winter is coming.", the motto of House Stark.

The Challenge "Game of Thorns" is another reference to Game of Thrones.

Snow White and the Seven Dwarves
Sometime through the storyline you will get a mission from Scooter to find his cannibalistic girlfriend Laney White, when you find her she is shacked up with 7 midgets. This a reference to Snow White and the Seven Dwarves. If you enter the back room where you find her, you will see 7 beds and a double bed for her.

The challenge "Fairest of them all" is a reference to the story.

XKCD
Upon completing Hyperion Contract #873, you will receive a Morningstar sniper rifle that the Hyperion recording describes as the XKCD experimental weapon. This weapon taunts you when you have it equiped to your hot switch with phrases like, "Great, now you're wasting ammo" or "Good shot, murderer"

3:10 to Yuma
The mission "3:10 to Kaboom" is a reference to the movie 3:10 to Yuma.

Ace Ventura
The challenge "When Nature Calls" is the title of the second movie, Ace Ventura: When Nature Calls.

Annoying Orange
The Gunzerker has a skin titled "Annoying Orange," a possible reference to the YouTube/Cartoon Network show of the same name.

Apocalypse Now
Buzzard pilots will occasionally sing the first phrase of the "Valkyrie" motif from "Der Ring des Nibelungen", an opera by Richard Wagner, alluding to the famous helicopter scene from Apocalypse Now.

Arrested Development
An NPC in Sanctuary who sells newspapers will say, "There's always money in the news stand!" This references how "There's always money in the banana stand.", speaking about the Bluth Company's Banana Stand from the series Arrested Development.

There is a Gunzerker skin named, "I Blue Myself" in reference to line spoken by Tobias.

Bad Boys
The challenge "Ride Together, Die Together" is a segment of the motto of main characters Mike Lowery and Marcus Burnett (Played by Will Smith and Martin Lawrence, respectively). "We Ride Together, We Die Together - Bad Boys For Life"

Batman
There is a location in The Fridge know as the "Rakk Cave." Rakkman inhabits this area and carries similar weaponry to the character Batman.

In addition, elements of the mission "The Bane" including the opening ECHO recording may be references to the character from the Batman comics and the recent Christopher Nolan film interpretation of the Bane character.

Batman Forever
On play-through 2 the character known as Rakkman is renamed to "Rakkman Forever." A reference to the film, Batman Forever.

Blue Gender
Blue, the unusally large cystalisk encoutered in Caustic Caverns, is a refrence to the alien creatures of similar shape and with the same name as in the anime series Blue Gender.

The Boondock Saints series
By completing a specific quest you will earn a shotgun or a shield that references the movies "The Boondock Saints" and "The Boondock Saints 2" saying 'They should have stopped at one.' or 'The second is better.', respectively while referencing the main characters tattoos: "Veritas and Aequetas".

Breaking Bad
There is a head skin for Salvador called 'Breaking Bald', which makes Salvador look like the protagonist, Walter White, from Breaking Bad.

Occasionally psychos will yell "I am the one who knocks!" while in combat. This is another reference to Breaking Bad. The original line, as delivered by the main character, Walter White, is: "You clearly don't know who you're talking to, so let me clue you in: I am not in danger, Skyler. I am the danger. A guy opens his door and gets shot, and you think that of me? No! I am the one who knocks!"

Citizen Kane
Upon completing the Slab's initiation ritual, a NPC called Sarcastic Slab will appear and start clapping in a fashion simillar to the Citizen Kane Slow Clap Meme.

Chappelle's Show
The challenge "Eff Yo' Couch" is a phrase coined by Dave Chappelle during the skit "Charlie Murphy's True Hollywood Stories" where he describes the events that took place when he invited Rick James into his home. During the reenactment, Dave Chapelle (Acting as Rick James) ground his feet into a white couch while shouting the phrase.

A Clockwork Orange
The Vladof sniper rifles use Nadsat slang terms in their names such as Droog, Dobby and Horrorshow.

Community
NPCs in Sanctuary will sometimes use the phrase "Streets ahead.", coined by Pierce in Community.

Cool Hand Luke
The challenge "Failure to communicate" is a reference to the line "What we've got here is failure to communicate" uttered by the prison warden, Captain.

Crouching Tiger, Hidden Dragon
The challenge "Crouching Tiger, Hidden Assault rifle" is a reference to the movie title.

CSI: Miami:
There will be a quest in sanctuary where the player is required to find evidence of someone's murder.

The quest is called "We won't get fooled again". This is the name of the theme song of the T.V. show itself.

Die Hard
Salvadors skill "Yippee Ki Yay" is a reference to the same phrase in Die Hard.

Dirty Harry
Salvador's skill "5 Shots Or 6" is a reference to the famous "Do you feel lucky?" monologue.

There is a pistol with red text that reads: "Did I fire six shots, or only five? Three? Seven. Whatever." It is a reference to the same monologue above. It is usually found on a large magnum styled weapon similar to Dirty Harry's gun.

Doctor Who
A random citizen will sometimes say "I'm missing the new episode of Constable What!", a parody of Doctor Who.

After blowing up the dam in "Hell Hath No Fury" Jack will list four names of workers killed in the flooding, all of which are the names of the first four actors playing the Doctor in Doctor Who. These are William Hartnell, Patrick Throughton, Jon Partwee, and Tom Baker.

At the beginning of the game Claptrap says "allons-y", which the 10th Doctor from Doctor Who is known to say.

The NPCs constantly knocking on walls in Sanctuary seem to be doing so in a similar beat and fashion to the subliminally-controlled humans in the Doctor Who episode "The Sound of Drums." The Master also refers to Captain Jack Harkness as "Handsome Jack" in that episode.

ECHOs found in Lynchwood bandit's named 'John' and 'Barrowmen' reference Doctor Who and Torchwood actor John Barrowman, who played character Jack Harkness.

There is a skin for Maya called "Rose Tailor", a play on the character Rose Tyler from Doctor Who.

The Dark Knight
By doing a certain quest, you can unlock a skin called "Why So Serious?". It is green, white, and purple and is a reference to Heath Ledger's portrayal of the Joker in the film The Dark Knight.

Rakkman also has an ECHO recorder titled "The Rakk Knight".

Dazed and Confused
The achievement references an early 90's stoner comedy 'Dazed and Confused' (itself a reference to the Zeppelin song of the same name from their debut in 1969) set in the 197o's around a group of high school students, portraying their lifestyles, antics and character traits particular to the era.

Firefly
In Liar's Berg, one of the buildings is named "Fillion's Ammunition & Arms". Nathan Fillion is an actor who was in the show Firefly which had a similar 'space western' setting.

Flash Gordon
A weapon has red text that reads: "What play thing can you offer me today?" This is a reference to the movie Flash Gordon with the line "Klytus, I'm bored. What plaything can you offer me today?"

Flight of The Conchords
After completing the fifth circle of death for Innuendo-bot 5000 in Ore Chasm, the final reward is a sniper rifle called Monstrous Chere-amie with the caption 'Je suis enchante, Ou est la biblioteque?' referencing the song Foux du Fafa a song by Flight of The Conchords.

Full Metal Jacket
In the challenges section, "This is My Rifle..." and then "...this is My Gun" was made from the Rifleman's Creed, a Marine Corps doctrine, which was used in the film Full Metal Jacket in this fashion.

G.I Joe series
Zer0's "Eyes of a Snake" skin is a reference to Snakes Eyes from the G.I Joe series.

Zer0's "Gh0st" head bears a striking resemblance to Snake Eyes.

The achievement called "Knowing is half the battle." which was a phrase used during the Public Service Announcement segments at the end of the 1980's G.I Joe cartoon show.

Godzilla series
After defeating Bloodwing if you return to the area of the fight again, Bloodwing won't be there. Instead there is a another creature called "Son of Mothrakk" referring to Mothrakk from the First Game, which in turn is a reference to Mothra from the "Godzilla" franchise.

Dukino's Mother, from the "Demon Hunter" quest, is very similar to Skagzilla from the original Borderlands. In addition, her large shoulder spikes resemble those seen on the adaptation of Godzilla in the 1998 film.

The Good, the Bad, and the Ugly
While in Tundra Express, Mordecai gives you the mission The Good, The Bad, and the Mordecai, which is a reference to the Clint Eastwood western film The Good, the Bad, and the Ugly. The ending of the mission also parallels the ending of the film.

Iron Chef America
Midget rats say "Allez cuisine." This is in reference to the show Iron Chef America In which the chairman introduces the 'secret' ingredient followed by the saying to start it off.

Joe Versus the Volcano
When completing the "Geary " Easter Egg, and continuing through the obstacle course, you will reach a Lance Chest, along with completing the challenge "Vault Hunter v. The Volcano".

King Kong
There is an enemy in Eridium blight named "King Mong" referencing the movie King Kong.

Furthermore, the challenge "'twas slag killed the beast" is a reference to the ending line of King Kong "'twas beauty that killed the beast."

Kiki's Delivery Service
There is a Tediore manufactured shotgun labeled Extra Large Deliverance. The name of the gun and the red text which reads "Kiki got a shotgun" is a reference to the movie Kiki's Delivery Service. When it is thrown to be reloaded, the gun also flies in a straight line or homes in on an enemy and leaves a trail, similar to how Kiki's flies on her broom.

Kuffs
The Gunzerker Skill "No Kill Like Overkill" contains a quote reading "I'm looking for a really big gun that holds a lot of bullets". This is a line spoken by Christian Slater's character in the 1992 film Kuffs. The gun salesmen's response is "God Bless you, young man".

Law & Order
There is a weapon called law and a shield called Order. Both items benefit from the player having both. The red text on Order is "Chung-gunk!" a reference to the "Law & Order sound." Sometimes the sound is refered to "Chung-chung" or Gunk-gunk."

The Lion King
Somewhere in the Wildlife Exploitation Preserve, there is a skag named "Tumbaa" and a stalker named "Pimon". This is a reference to Timon and Pumbaa from the movie The Lion King.

Logan's Run
The legendary repeater "Logan's Gun" with the red flavor text "Gun, Gunner!" ("Run, runner!") references the film Logan's Run.

Mad Men
There is a skin for Salvador called "Smoke Gets In Your Eyes" which is a reference to the title of the first episode of Mad Men.

My Little Pony: Friendship is Magic
In the credits, a member of the game's production team, Chris Francis, says thanks to

"his adorable Fluttershy ", one of the characters from the TV show.

The Matrix
There is a pistol with red flavor text that reads: "Dodge this." A reference to the famous line in The Matrix.

Mighty Morphin' Power Rangers
The quest "Mighty Morphin'" is a reference the the 90s children's show Mighty Morphin' Power Rangers, the original series from the Power Rangers franchise.

The Muppets
The Challenge "It's Not Easy Looting Green" references Kermit the Frogs song "Bein' Green."

Mystery Science Theater 3000
The character "Flanksteak" is a reference to Bold Flanksteak, one of the numerous names given by Mike and the bots to the beefy main protagonist in the "Space Mutiny" movie.

Oprah
While in combat, Axton can occasionally say "And YOU get a bullet, and YOU get a bullet! EVERYONE gets a bullet!" a reference to Oprah's energetic nature and giving audience members gifts.

Party Down
Some NPCs in Sanctuary ask the question "Are We Having Fun Yet?", a line actor 'Adam Scott' delivers with chagrin in the STARZ comedy series 'Party Down'.

Predator
Salvador's skill "Sexual Tyrannosaurus" is a reference to the same phrase said by Blain Cooper in the early scenes of the movie.

Salavadore's skill "Ain't Got Time to Bleed" was a line spoken by Blain Cooper.

The challenge "You're One Ugly Mother..." is a reference to what Major Alan "Dutch" Schaefer says when he sees the Predator unmasked.

The achievement, "Unseen Predator" could be a reference to the Predator's cloaking device since the icon shows Zero activating his invisiblity.

The E-Tech SMG name, "Plasma Caster," is the official name of the Predator's shoulder cannon.

In the loading screens, one of the tips refers to stalkers, saying "If it bleeds, you can kill it, etc.," alluding to one of Major Alan "Dutch" Schaefer's lines from the movie. It's also worth noting that stalkers can turn invisible so long as their shields aren't depleted.

The Princess Bride
Some higher level rat enemies are labeled as "R.O.U.S", a reference to the rodents of unusual size. Additionally, one of the assasins from the "Assassinate the Assassins" quest, Assassin Rouf, is a gigantic rat.

The Berserker's 'Inconceivable' skill is a reference to a line frequently stated by one of the characters from The Princess Bride.

Pulp Fiction
The challenge 'Say Watt Again!' is a reference to the crime film Pulp Fiction's character Jules Winnfield who uses this line during an interrogation.

Reservoir Dogs
Axton's skin, "Mister Blonde" is a reference to the Quentin Taratino movie where all the hitmen were named after colors, including a Mister Blonde.

Rocko's Modern Life
Far into the story, Brick will give you a mission named 'Rocko's Modern Strife'. This is a reference to the cartoon Rocko's Modern Life.

Saturday Night Live
One of Maya's skins, "Light Urple", is an answer given by one of the contestants in SNL Celebrity Jeopardy when asked to give the only color that ends in "Urple".

Serenity
One of Zero's available costume skins is "Leaf on the Wind", which is a reference to something Alan Tudyk's character Wash says during the final airborne battle.

Se7en
When opening a randomly spawned cardboard box in The Dust, Handsome Jack will yell: 'What's in the box? What's in the box??'. There is a female head in the box and a gun. The gun can be named: 'Neutralizing Gwen' or 'React Gwen's Head'. A reference to the movie Se7en.

Shaun of the Dead
One of Maya's available costume skins is named "Slice of Fried Gold" which is a reference to zombie-action-comedy flick Shaun of the Dead.

Silent Night, Deadly Night 2
Sometimes after killing an enemy in gunzerker mode, Salvador will shout out "Garbage day!", a reference to an infamous line from the movie and internet meme.

The Simpsons
In Sanctuary, an NPC can be heard saying "I must go, my people need me.", a line similar to one spoken by Poochie in the 8th season episode "The Itchy & Scratchy & Poochie Show".

Star Trek
The "Greenblood" Siren skin is a possible reference to the common insult to Vulcans in the Star Trek series.

The phrase "Welcome back from the undiscovered country." said by the New-U station when reviving is a reference to the 6th film from the original series.

Zer0 has a skin called "Red Shirt," A reference to the colloquial name given to starfleet security officers and the color uniforms they wear. it is unknown if the skin causes the player to die first or more frequently

Star Wars
Zero's Blast Helmet could be a reference to the training helmet used by Luke Skywalker in a A New Hope during the training session with Obi-Wan.

The challenge "That's Impossible, Even for a Computer" is the line said by Wedge Antilles when the Rebel forces were planning the attack on the Death Star during A New Hope.

Talladega Nights
The challenge "If You're Not First, You're Last" is the catchphrase of main character and NASCAR star Ricky Bobby.

Teenage Mutant Ninja Turtles
The side mission "Splinter Group" includes multiple references to TMNT. The mission involves delivering a pizza to a sewer system with four mutant inhabitants: Lee, Dan, Ralph, and Mick. Once the mutants realize the player isn't "June", they'll attack. At the end of the area there is a subway-style room with a couch and a TV (itself another reference to TMNT), a set of four switches, and five lights on the wall. If all of the lights go green, a boss rat called "Flinter" will appear.

Each switch controls two sets of lights. Each press of the switch will change the lights in that group from red to green and vice versa. From all red lights, pull the floor lever twice, puch the wall switch once, then turn the pipe knob and switch the TV three times each.

Zero can use an unlockable skin called "Mutant" that places a blue stripe on the Assassin's head. The skin is a reference to Leonardo, who also uses a katana and wears a blue headband.

The QR Code on the pizza box in Moxxi's place scans as "Wise man say forgiveness is divine but never pay full price for late pizza.- Captain Picard". The misquote is from the first TMNT movie (Captain Picard never said this).

The Little Mermaid
Axton's skin, "Unda Da Sea" is a reference to the song sung by Sebastian in the movie.

They Live
Salvador's skill "All Out of Bubblegum" is a reference the phrase "I've come here to chew bubblegum and kick ass. And I'm all out of bubblegum," which is first said by "Rowdy" Roddy Piper in the movie "They Live."

Tombstone
Salvador's Gun Lust skill "I'm Your Huckleberry" is a line often spoken by Doc Holliday in the film.

Top Gun
At Ellie's Garage in The Dust, you receive a quest from a Buzzard Pilot named Loggins. This is a reference to the movie Top Gun, and how one of the prominent musicians in the film is Kenny Loggins. When you turn in the mission he will say "You can be my wingman any time."

The same character, Loggins, will say several quotes from the movie when spoken to.

On the Top Gun film soundtrack one of the main artists is Kenny Loggins. Within the dialogue of Loggins he quotes "Take My Breath Away" and "Danger Zone", both of which are tracks from the album (the latter having actully been performed by Kenny Loggins).

Tora! Tora! Tora!
Buzzards will occasionally shout "Tora! Tora! Tora!" (Japanese for "Tiger! Tiger! Tiger!"). Historically, "Tora" was a code phrase used by the Japanese during their attack on Pearl Harbor in 1941. The phrase was later used as the title of a movie about the attack.

Transformers
Claptrap will sometimes say to the player, "Minion, roll out!", a reference to Transformers.

The JET varient of Loaders are also a reference to Transformers, as they share the same color scheme and capabilities as one of the main Decepticons, Starscream.

Yu-Gi-Oh
When using Zer0's Decepti0n, he sometimes says, "How hilarious. / You just set off my trap card -- / Your death approaches." in reference to Yu-Gi-Oh, and the phrase was often used on the Internet.

Zardoz
There is graffiti in the Bloodshot Stronghold that depicts Marcus vomitting up guns that reads "Marcus Gunbringer". This is a reference to the 1974 film "Zardoz".

Altered Beast
When the player is respawned, one of the phrases spoken by the New-U station's AI is "Rise from your grave." This is a direct reference to the same phrase spoken during the intro of Altered Beast.

There is a Gunzerker class mod called "Altered Beast".

One of Maya's skills in the Harmony tree has the description, "Rise from your grave."

Amnesia: The Dark Descent
Captain Flynt will drop "Flynt's Tinderbox", a Bandit pistol with flavour text that reads: "Good for starting fires." This is a reference to the popular psychological horror game, Amnesia: The Dark Descent, which has items called 'Tinderboxes' with the same description.

Borderlands
There is a weapon with red text that reads: "I infrequently perish." This is a reference to the line Mordecai says when he gets downed in the first game, "I never die."

When meeting Mordecai for the first time in Santuary after Bloodwing's death, Lillith and Roland can be heard talking about an instance when Mordecai got shot in the shoulders and sent bloodwing to fight some bandits, but bloodwing fails to do so until Mordecai faces the bandit. A possible reference to the original Borderlands in the instance that bloodwing can not attack enemys that Mordecai can not see.

Call of Duty series
The challenge "Call of Booty" and Axton's skill "Duty Calls" are references to the Call of Duty series of games.

Zer0's head "Gh0st" is similar to that of the character Ghost from Modern Warfare 2.

Demon's Souls
Marcus Kincaid's gun vending machines will sometimes see you off with "Don't die, I need your business!", an echo of what Blacksmith Boldwin says to you in the Nexus.

Dark Souls
In the Caustic Caverns, there is a small island with an NPC named Solitaire sitting on a ledge in front of a bonfire. A white phantom is sitting in front of the bonfire. This is a reference to the video game Dark Souls, with Solitaire being a reference to the knight Solaire of Astora.

Donkey Kong
There is an enemy named "Donkey Mong" who throws barrels and wears a tie. He is a reference to the game and and the character of the same name.

The achievement called "Definitely an Italian Plumber" whose icon is a barrel makes a reference to Donkey Kong as well.

Driver: San Francisco
An NPC in Sanctuary can occasionally say "I was playing this Echo Sim where you could jump into trucks with your mind. It's pretty much the best thing ever." This is a reference to Gearbox writer Anthony Burch's love for Driver: San Francisco.

Dwarf Fortress
Salvador's "Boatmurderer" head, a dwarvern-style beard and spiked mohawk, is a reference to Boatmurdered, an infamous Dwarf Fortress succession game from Something Awful.

Fallout series
There is a Bandit Shotgun called Thre Dog. The red text says 'Because one barrel ain't enough, and two is too few.' This is referencing the character Three Dog the radio broadcaster from the Bethesda game Fallout 3. Both of these reference the song "One" by the band Three Dog Night.

The skin "Vault Dweller" for the Siren is a refrence to the outfits worn by the members of the vaults from the Fallout series. It follows its color pattern with blue body and yellow highlights.

Final Fantasy Series
In the Challenges, there is a challenge in the melee section called, "A Squall of Violence." This is a reference to Squall Leonhart from Final Fantasy VIII, who used a gunblade, which was a gun that had a sword on the end. The challenge is for killing enemies with melee attacks using a bladed gun.

Half-Life series
In the quest to put the power of the Happy Pig Motel, the objectives contain "Find Steam Valve", and "Find Gearbox". This is a reference to Valve, and its platform Steam, and Gearbox, the developer. A similar set of objectives appeared in a stage of one of the first gearbox games, Half Life: Opposing Force.

Halo Series
When Zer0 kills someone, sometimes he will say "assassins never die" a nod to the phrase "Spartans never die"

The ending of Borderlands 2 parrellls the first Halo games ending.

Mario Kart series
The "Blue Sparks" vehicle challenge is a reference to the Mario Kart series.

Legend of Zelda series
In Sanctuary, Crazy Earl will say "It's dangerous to go alone, jerkwad!" This is a reference to the famous Legend of Zelda quote.

Metal Gear series
If you climb the volcano in Eridium Blight, you can sometimes get a face customization item off of Geary who just wanders in a small area. The item is called Metal Fear which is a reference to the Metal Gear series.

Zero's default skin is called "Zero's Sneaking Suit," a reference to Snake's Sneaking Suit, which also turned invisible.

When he has been seen, Zer0's display will sometimes show an exclamation point -- a reference to the Metal Gear series of games.

Axton's head skin "Medic Mantis" is a reference to Psycho Mantis from the Metal Gear series.

The Thief Rats, on occasion, call out "The fear!" when attacked. This is a reference to the same named boss from Metal Gear Solid 3.

Some of the Crimson Raiders will describe Sanctuary as being "just outside heaven for soldiers like us. Always something to fight." References the ideals behind the founding of Outer Heaven.

If you visit Dr. Zed's in Sanctuary, ocassionally the citizen inside will say "I feel asleep..." This is a well known line form the original Metal Gear on the NES.

Minecraft
There are several references to Minecraft at the Caustic Caverns location. Some references include destructible blocks from the game, Creepers, and Minecraft-themed customization items.

There is a gun with red text that reads: "Also try Minecraft!" Minecraft is know to promote other games in a similar manner using "splashes" when the game launches. The gun shoots projectiles in a 3x3 square formation.

There is another gun with the title "Longbow", which is a scopeless sniper rifle that shoots bullets which leave a pixelated trail, just like arrows in Minecraft.

Postal series
Occasionally upon dying, bandits will exclaim "I regret everything!". This is likely a reference to the cult series of games by Running With Scissors, wherein the protagonist Postal Dude uses the catchphrase "I regret nothing!", often before comitting suicide, murder, or both.

Resident Evil series
One of the challenges is called "Waddaya Buyin'?", this is most likely a reference to Resident Evil 4's merchant trader whose dialogue consists of: "Waddaya Buyin'?" and "Waddaya Sellin'?"

Saints Row series
Some Sanctuary NPCs will mention an ECHO sim about "The Gang That Wore Purple," a pretty obvious nod to the 3rd Street Saints of the Saints Row games.

S.T.A.L.K.E.R. series
Thief Rats act and look very close to Snorks from the STALKER series, down to their constant jumping and when attacking the player large red slashes appear on the screen, much like in STALKER.

Skyrim
In Sanctuary, NPCs can occasionally say "I used to be a Vault Hunter like you, until I took a bullet to the knee." This references Skyrim's guard arrow-in-the-knee meme.

Roland also references the line when he first meets the Vault Hunters, saying "I used to be a Vault Hunter like you, until I founded the Crimson Raiders."

Warhammer 40,000
There is an assassin skin mod called "Ultramarine", referencing the Ultramarines, a Space Marine chapter with the same colors as the skin: blue, white, and gold, although the skin has a dirtier look.

It is possible that the Bandit weapons names are a reference to the Ork weapon's names in Warhammer 40K.

The Emperor SMG's red text, "you know... for him" is a reference to the Warhammer 40,000 universe, where the Imperium of Man uses "For the Emperor!" as a battle cry.

X-Men
Sometimes, Goliaths will say, "Welcome to die!", a reference to the infamous line spoken by Magneto in the 1992 X-Men arcade game.

Avenged Sevenfold
The challenge, "Critical Acclaim" is a refrence to their first song of the album, "Avenged Sevenfold"

Black Betty
The challenge "Woah, Black Betty" is a reference to the song Black betty by the band Ram Jam.

Drake
At one point, Tiny Tina says "Shorty, you da best. You da you da best." This references the song "Best I Ever Had" by rapper Drake.

Duran Duran
The side mission "Hungry Like the Skag"'s name is a reference to Duran Duran's song "Hungry Like the Wolf".

Led Zeppelin
The achievement, "Phased and Confused" is a reference to a signature song, 'Dazed and Confused' by Led Zeppelin, that when performed live was often extended with improvisations featuring Page's bowed guitar workouts. The song debuted on their first self-titled recording in 1969. Or the movie "Dazed and Confused"

The Ink Spots
Miss Moxxi's Heart Breaker has red text that reads "I don't want to set the world on fire..." A reference to the song of the same name by The Ink Spots.

There is a challenge with the same name for setting enemies on fire.

Purple Rain
The challenge "Purple Reign" is a reference to Prince's song, album, and film, "Purple Rain".

Wilhelm Scream
The achievement "Wilhelm Screamed" is a reference to the Wilhelm Scream.

Fade to Black
Axton's skin 'Fade To Blue' is a reference to Metallica's song 'Fade To Black.'

Foux du Fafa
There is a gun with red text that reads "Je suis enchante, Ou est le bibliothque?" this is a reference to the song Foux da Fafa by Flight of the Conchords.

In the Hall of the Mountain King
Sometimes while Gunzerking, Salvador will hum Edvard Grieg's famous "In the Hall of the Mountain King."

I Shot the Sheriff
In the mission Showdown where you have to face off with the sheriff of Lynchwood, there is an optional objective that reads, "Do not shoot the Deputy". This is a reference to the song "I Shot the Sheriff" originally by Bob Marley and The Wailers (but made popular by Eric Clapton). The chorus of the song is, "I shot the sheriff, but I did not shoot the deputy."

Never Gonna Give You Up
When killing a Psycho, they may say "Never gonna give you up..." This is an allusion to the popular Rick Astley song of the same name.

I Believe I Can Fly
Sometimes when phaselocked, a bandit will say, "I believe I can fly." This song was in the mid 1990's movie "Space Jam".

Bruce Lee
Zer0'skill "Be Like Water" is a reference to Bruce Lee famous quote "Be like water".

Isaac Asimov
The PDA system in hyperion areas tell the loaders to "Remember your three laws..." refrencing the three governing laws of the robots created by Asimov. These three laws were also used in the movie "I, Robot."

Loaders, upon entering combat, will sometimes say "First Law Disabled." A refrence to the first law of robotics; "A robot may not injure a human being or, through inaction, allow a human being to come to harm."

Jean-Claude Van Damme
The challenge "The Van Is Damned" is a play on his name.

Mobil
The Catch-a-Ride logo is a play on the gas company Mobil's logo.

Samuel Butler
A grenade called the Leech has red text that reads: "A skilful leech is better far, than half a hundred men of war." This is a quote made by Samuel Butler.

Sarah Palin
There is a gun with red text that reads: "Don't retreat, instead reload!" This is a reference to Sarah Palin's similar phrase.

Verizon Wireless
The challenge "Can you hear me now" is a reference to the popular Verizon Wireless ads.

Wasteland Panda
There is an abandoned gas station in The Dust with a slot machine inside; on the wall to the left of it is a stencil of the panda from "Wastelander Panda."

United States Postal Service
The mission Neither Rain nor Sleet nor Skags is a reference to the unofficial motto of the USPS.

Cool story, bro
After getting a kill, Axton will occasionally say "Cool story, bro." This is a reference to the phrase used in response to a lengthy, off-track, or obviously fake story.

Similarly, the woman being talked at by a drunk outside Moxxi's will sometimes respond with "Super cool story, bro."

Killing Handsome Jack at the end of the game gives the "Cool Story, Bro" achievement.

Double Rainbow
The achievement "What does it mean?" is unlocked when seeing a double rainbow in the skies of The Highlands. This is a reference to a viral video of someone overly excited about a double rainbow.

Psychos will also occasionally shout "What could it all mean?" which is likely a reference to the "Double Rainbow" video.

Dragon Ball Z
The dials on each radio on Pandora show each hundred from 100 to 800. What should be "900" is acually "9001" in reference to the "It's over 9000" meme.

Leeroy Jenkins
The challenge "JEEEEENKINSSSSSS!!!" is part of the famous phrase where he shouts his name and runs blindly into a dungeon in World of Warcraft.

Neil DeGrasse Tyson Reaction
While fighting a badass enemy after finding Lilith, she will sometimes say "Watch out, we've got a badass over here." This is a reference to the Neil DeGrasse Tyson meme of a similar title.

Shoop da Whoop
Constructors, before using their laser attack, will occasionally say "I'm charging mah lazer." a phrase associated with the "Shoop da Whoop" meme.

Super Cool Ski Instructor
One of the loading screen tips will say "if you fight a fire skag with a fire gun, you're gonna have a bad time." This is a reference to the South Park ski instructor meme.

U Mad?
The challenge 'U (No)mad bro?' Is a reference to the "U MAD?" internet meme.

Xzibit Yo Dawg
One of the challenges is called "Yo Dawg, I heard you like challenges." in reference to the Xzibit meme.

Other

 * When rescued in Liar's Berg, Sir Hammerlock mentions the town was once full of "hustle and/or bustle", a possible reference to Homestar Runner.
 * Inside the Bloodshot Stronghold, three red eyes may be seen ("bloodshot eyes"). This may be a reference to a Korean webtoon called "Tower of God", where said red eyes are the symbol of the ruling government.
 * At the end of the mission Clan War: First Place Ellie says, "After this red harvest, you'll be the last one standing with a fistful of dollars. Yo jimbo." Fistful of Dollars is a Clint Eastwood western that is based on a samurai film called Yojimbo (both of which are based on the Dashiell Hammet novel Red Harvest) and Last Man Standing is a similar movie starring Bruce Willis.
 * "Good things kill in threes." is a possible reference to the Rule of Three.
 * In Lynchwood, there are a series of missions: "If you give a skag some medicine.. he's going to want some food" - these are based on the children's picture book "If you give a mouse a cookie."
 * In Southern Shelf, north of the exit to Three Horns - Divide right across the gap in the ice is a floating barrel that reads 'Gamerson Whiskey' which is a reference to the Jameson Whiskey commercials.
 * In the Clan War series of quests there is a mission called "Clan War: Follow the Rainbow". When first gotten its description says nothing but, "Hearts, Stars, and Horseshoes...". This is the beginning of the lucky charms Jingle.