Rat

Rats are a humanoid faction appearing in Borderlands 2. Whereas bandits inhabit the wastes of Pandora the Rats occupy the urban areas or ruins of the planet.

The Rats wear gas masks, as they once lived in toxic mines and tunnels. Over time they mutated, with some growing long claws and shrinking in size and stature, while the Rats as a whole have become cannibalistic. When they collect people to be sacrificed and eaten, midgets and other bandits are often on the menu. The masks have become a sign of their status, and they wear them now for ceremonial purposes.

Very much like actual rats, this faction will grab and make off with loot. This may lead to interesting decision points as a player weighs the benefits of defeating a threat or pursuing a rat which has acquired a valuable loot item. Defeating a hoarding rat will result in a burst of scattered loot. Additionally, due to their cannibalistic nature, they can regain health by devouring corpses.

Normal Mode
Uses the names on the left.
 * Tunnel Rat/Cannibal Rat - The basic and most common type of Rat encountered on Pandora. They are not very durable and as such will try to stay as far back from their enemies as possible, shooting at them with assault rifles and ducking and weaving away from enemy fire. In the case that an enemy gets too close, they will either leap at them or hit them with a claw swipe to knock them away. If there is any loot on the field, they will run over to it and pick it up. If left alone long enough after picking up loot, they will bury it and the loot will become unrecoverable.
 * Field Rat - A stronger, tougher, faster and more evasive version of the Tunnel Rat and like Tunnel Rats, they try to stay back from their enemies and pepper them with assault rifle fire. However, unlike Tunnel Rats, occasionally they will go in for a quick melee strike which is usually done via a powerful long-distance leap that is capable of knocking enemies back. They will also stop to pick up any loot they find on the battlefield.
 * Rat Thief/Rat Bastard - Unlike other Rats, Rat Thieves have almost no interest in fighting, instead, they are interested in pilfering a sizeable chunk of money from unsuspecting travelers. Rat Thieves move quickly, quietly and often from behind their targets. If a Rat Thief is successful in his attempt to steal money, he will quickly scamper off to bury his newfound treasure, like other Rats. If he successfully buries the money he has stolen, it will become unrecoverable. The money can be recovered if the Thief is killed before he buries the money. Close_up_of_Rat_Thief.jpg
 * Midget Rat/Runty Rat - Diminutive and substantially weaker versions of Tunnel Rats. However, unlike Tunnel Rats, they tend to close in on their targets a little bit and their heads are fairly large, making for easier critical hits.Their small size and fast movement speed makes them hard to hit regardless.
 * Lab Rat/R.O.U.S - Lab Rats are almost polar opposites to the other Rats: they are slow moving and have very high health. They don't pick up loot or items on the ground, and attack mainly from close range. The only time a Lab Rat will attack from a range is when he cannot reach a target and at that point will begin to toss a Buzzaxe in a manner similar to a regular Psycho. If they get close to their target, they will unleash a devastating eye-laser attack that can quickly destroy shields and wearers alike. As they advance towards their target, they will cover their face with their non-mutated left arm, making it harder to score a critical hit. Shotguns will be effective in hitting their head even if blocked by their hands thanks to the pellet spread.Sniping_Lab_Rats.jpg
 * Miner Rat/Digger Rat - A slightly stronger version of the Tunnel Rat found in the Tundra Express and the dig site in Lynchwood. They can tunnel underground, reappear topside to strike, and then dive back under to move to a different location. They cannot be hurt while underground.
 * Sewer Rat - Rats spawned during the Pete the Invincible fight if the valve to the left of the Raid Post in his arena is used. Each time the valves are used, their levels are increased by 3, with a cap of 66.

True Vault Hunter Mode

 * Plague Rat - A rat that crawls around on all fours very quickly (similar to a rat thief/rat bastard), it slashes at its prey with acid soaked claws causing corrosive damage upon successful hits.

Badasses

 * Loot Midget Rat
 * Assassin Rouf
 * Dan, Lee, Mick, Ralph - Named Rats in Bloodshot Stronghold
 * Laney White
 * Bloody, Crabby, Creppy, Dirty, Greedy, Sleazy, Tipsy - Named Midget Rats in The Fridge
 * Mortar
 * Flinter

Quotes
Normal On taking damage Stealing an item Dying
 * Allez Cuisine!
 * I'm so HUNGRY!
 * I can tassste you already!
 * Another morsssel for the fridge!
 * Food for the Family!
 * Ssscream!
 * Rip and chop, RIP and chop, RIP AND CHOP!
 * Not in the lab...Not in the lab! (Lab Rat)
 * Look into my eyes (Lab Rat)
 * Open your Eyesss (Lab Rat)
 * Optic Blast! (Lab Rat)
 * Windows to the SOUL! (Lab Rat)
 * Omnomnomnumnumnum (said very rapidly)
 * Whats Cookin'? (when hit by fire damage)
 * What'ssss that ssssmell? (Lab Rat)
 * You don't need thisss anymore!
 * Thanksss, brother!
 * It'sss mine now!
 * Corpsssse robbing!
 * I sssmell deliciousss! (when killed by incendiary elemental damage)
 * Ratsss!
 * One less...Mouth to feed...
 * Not on an empty stomach...
 * The food killed me!
 * Killed...By a morssssel...
 * Killed...By sssome dumbassss!

Trivia

 * In True Vault Hunter Mode, the Lab Rat's name changes to R.O.U.S, an acronym for Rodents Of Unusual Size. This is a reference to the strange rats that inhabit the fire swamp in the 1973 novel and 1987 movie The Princess Bride.
 * There are 7 named Midget Rats, a play on the Seven Dwarfs of Snow White Fame.