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.
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/movie by--respectively--J. R. R. Tolkien/Peter Jackson: "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.
Sometimes in Sanctuary a random Crimson Raider will say, "This is no planet for old men.", referencing the movie No Country for Old Men.
Psychos will occasionally shout out "I am immortal!" a reference to the movie Highlander.
Buzzards 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.
Buzzards will also 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.
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.
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 is named: 'Neutralizing Gwen' or 'React Gwens Head'. A reference to the movie Se7en.
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.
After completing the quest "The Cold Shoulder" for Scooter in the Fridge, if you enter the room where Laney emerged you are taken through an area filled with rats. At the end there is a location called the 'Rakk Cave' where you fight Rakkman, who throws boomerangs and uses smoke bombs. This is a reference to Batman and the Batcave. He will occasionally shout 'I AM...RAKKMAN!' In playthrough 2 he becomes "Rakkman Forever" referencing the Batman Forever movie. Further, when you approach the Rakkman's cave, the saturation of the world drops, referencing the art style of the "Arkham" series of Batman video games.
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. When you speak to him he will say 'I'm in the Danger Zone!' which is a reference to the song "Highway to the Danger Zone" (performed by Kenny Loggins) and will yell "Goose! GOOSE!" and when you turn in the mission he will say 'You can be my wingman any time.'
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.
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.
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".
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.
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.
There is an enemy in Eridium blight named "King Mong" a reference to the movie, King Kong and there is also an enemy named "Donkey Mong" who throws barrels and wears a tie. He is a reference to Donkey Kong and killing him awards you the "Definitely an Italian Plumber" achievement/trophy, a reference to Donkey Kong's original role as the antagonist of the original Mario game.
Ther 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".
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.
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.
Deukino'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.
There is graffiti in the Bloodshot Stronghold that depicts Marcus vomiting up guns that reads "Marcus gunbringer". This is a reference to the 1974 film "Zardoz".
Many of Salvador's skill names are references to action films, Including "Yippee Ki Yay" (Die Hard), "5 Shots Or 6" (Dirty Harry), "All Out of Bubblegum" (They Live), and "Sexual Tyranasaurus" (Predator).
Television
A crimson guard walking around Sanctuary will sometimes say "Winter is Coming", which is the motto of House Stark in the series Game of Thrones.
A random citizen will sometimes say "I'm missing the new episode of Constable What!''''" - A reference to what sounds like 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.
A possible pop culture reference: 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 the quest "Splinter Group" in which you have to pretend to be a pizza delivery man and deliver pizza to a sewer system in which 4 mutants that are color-coded with turtle shells obviously referencing Teenage Mutant Ninja Turtles. Their names are Lee, Dan, Ralph, and Mick. In the same quest, there is a room that has 6 lights on one of the walls, they'll be a combination of red and green. You must pull the 4 switches/levers in the room to turn all lights green. Once done, an enemy called Flinter will appear, which is another reference to Teenage Mutant Ninja Turtles.
There is a skin you can unlock for the assassin, called Mutant. It's the same colors of the Teenage Mutant Ninja Turtles.
There is a head skin for Salvador called 'Breaking Bald', which makes Salvador look like the protaganist, 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!"
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.
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.
Far into the story, Brick will give you a mission named 'Rocko's Modern Strife'. This is a reference to an old cartoon called Rocko's Modern Life.
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.
Zer0's "Eyes of a Snake" skin is a reference to Snakes Eyes from the G.I Joe series.
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 often used on the Internet.
An NPC in Santuary 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.
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".
While in combat, Axton can say "And you get a bullet, and you get a bullet. EVERYONE gets a bullet" a reference to Oprah
The Challenge "It's Not Easy Looting Green" References Kermit the Frogs saying "It Aint Easy Being Green"
Games
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 same citizen may mention an ECHO Sim called "The Gang that Wore Purple". This is a reference to a famous early twentieth century bootlegging gang in Detroit, the Purple Gang. The game series Saint's Row has a similar reference.
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-to-the-knee meme.
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.
In Sanctuary, Crazy Earl will say "It's dangerous to go alone, jerkwad!" This is a reference to the famous Legend of Zelda quote.
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.
Sometimes, Goliaths will say, "Welcome to die!", a reference to the infamous line spoken by Magneto in the 1992 X-Men arcade game.
One of the challenges is called "Waddaya Buyin'?", this is most likely a reference to Resident Evil 4's merchant trader whos dialogue consists of: "Waddaya Buyin'?" and "Waddaya Sellin'?"
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.
If you climb the volcano in Eridium Blight, you can sometimes get a face customization item off of Geary who just wonders in a small area. The item is called Metal Fear which is a reference to the Metal Gear series.
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 gas mask, '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.
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.
Inside the Caustic Caverns, there is Minecraft dirt. Walk up to the dirt, and melee it until it breaks. Then you will see Minecraft stone and coal, then you break that. Inside there is a bunch of Creepers: most normal but one Badass. Once defeated, the Creepers have a fairly high chance of dropping Minecraft-based skins and head customization items. In the same place, there are also gold Minecraft blocks, which drop money, and a new purple-colored ore block -- Eridium ore. When broken, it drops either Eridium or Minecraft-based customization items.
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.
Memes
The achievement"What does it mean?" is unlocked when seeing a double rainbow in the skies of The Highlands. Claptrap will radio in with a short dialogue - this a reference to the viral YouTube video of a person's amazed reaction to seeing a double rainbow.
Psychos will also occasionally shout "What could it all mean?" which is likely a reference to the "Double Rainbow" video.
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.
Constructors, before using their laser attack, will occasionally say "I'm charging mah lazer." a phrase associated with the "Shoop da Whoop" meme.
The challenge 'U (No)mad bro?' Is a reference to the internet meme 'U MAD BRO?'
Shooting Handsome Jack before he finishes his long tirade at the end of the game gives you the 'Cool Story, Bro' Achievement/Trophy. It is a reference to the phrase used in sarcastic response to a lengthy or off-track story.
A Psycho will sometimes say "Never gonna give you up..." when dying. This is a reference to the internet meme RickRoll'd.
On the side of any toilet stall found in Pandora, there will be a sign stating "Dook hut, No fapping." Fapping commonly refers to the meme interpretation of masturbation.
After getting a kill, Axton will occasionally say "Cool Story Bro."
One of the loading screen tips will say "if you fight a fire-enemy with a fire-weapon, your gonna have a bad time." a refrence to the south park ski instructor meme.
Inside bandit buildings, three red eyes may be seen. This may be a reference to a Korean webtoon called "Tower of God", where said red eyes are the symbol of the ruling government.
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."
There are several sniper rifles with such names as "Bolshy Bratchny", "Britva Bratchny" and "Gromky Droog". These are a reference to the nadsat language used in Anthony Burgess's novel, Clockwork Orange.
Occassionally, 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.
