Borderlands 1 Skin
If you have a save file for Borderlands 1 while playing Borderlands 2 you'll unlock characters skin from the previous game.
Easy "Not Full Of Monkeys" Challenge Levelling
"Not Full Of Monkeys" is a challenge that you meet by killing enemies with stationary barrels of any type. Well, with Gaige the Mechromancer DLC, you don't need the barrel! Anger a swarm of Rakks and summon the Deathtrap. They will rush you, and the Deathtrap will use it's laser to kill them. It counts as a stationary barrel this way. Try this on all flying enemies for some quick Badass rank!
Beating Terramorphous Solo *Requires 2 Controllers*
To beat Terramorphous if you don't have Xbox live or don't like joining sessions, all you need to do is set up a split screen game with your main character and a second character. The second character's gear doesn't matter because he will not be involved in any combat. First, get to Terramorphous peak and have your second character drop into his lair without summoning Terramorphous. Far to the right of the horn you use to summon Terramorphous there will be a small ridge at the very corner of the map before the open cliff meets the rock face. If you run to this ridge you will see that you can crouch and walk out behind it, completely blocking all of Terramorphous's attacks. (Note: You can still do this after Terramorphous is summoned however it is much more difficult.) This character will serve as a placeholder so that when your main character dies you will not lose your progress facing Terramorphous and he will not regain all his health. Now when you are ready drop your main character down and summon Terramorphous. From there you may use any strategy to wear his health down, however I would recommend finding helpful Legendaries such as the Unkempt Harold and The Bee shield before attempting this. When you die, you will simply respawn and be able to drop back down and keep fighting Terramorphous without his health regenerating. If you do not want to lose money when you die, give it all to the second character (who will never take damage) first so that you recieve free respawns from the New-U station.
Easy Thousand Cuts Farming
After accepting the quest "Rocko's Modern Strife" and heading to Thousand Cuts to start "Defend Slab Tower" you should notice that no foes will spawn in the area; as long as you don't progress through the quest. Since normal foes will no longer spawn, you are free to circle the area and loot every chest without being hindered by enemies. However, foes like one-armed bandits and loot midgets will still spawn. If you save and exit after clearing all the chests, you can simply accept "Defend Slab Tower" once again and clear them out as many times as you like with the same conditions as long as you don't complete the quest.
Easy XP during Tiny Tina's Tea Party Mission
At the end of Tiny Tina's Tea Party side quest you're required to lure a psycho named "Flesh Stick" back to her home. If you shoot and kill Flesh Stick rather than luring him back you'll reap a huge XP boost (750xp/kill on level 18 and around 1,800xp on level 17) which can be repeated by simply talking to Tiny Tina again and restarting the mission. This exploit works best during co-op play. where one person stations where Flesh Stick spawns and another at Tiny Tina. Doing so will enable you to repeat this process in quick succession until the game will no longer spawn Flesh Stick again. At this point you can run back to the start of the area, exit and return, or (faster), save & quit then reload the game. Doing so will allow Flesh Stick to respawn again.
2000 - 5000+ EXP / Min
While in the Tundra Express, complete all the optional quests for Tiny Tina that lead up to "You Are Cordially Invited: RSVP". This is a quest in which you need to lure Flesh - Stick into Tiny Tina's cave so that she can put him in a trap. The trick with this is to just kill him. Depending on what level you are (Level appropriate on first playthrough is anywhere from 1800-3000 exp per kill, playthrough 2 is anywhere from 2000-4500 per kill). Once you kill Flesh - Stick, just go back to Tiny Tina and restart the quest. If you are online and playing with friends, just have 1 friend stand by Tina while someone else stays by Flesh - Stick's spawn, and he will pop up instantly every time.
Unlimited fast badass ranks
Create a new character. Using a second controller, join the game as a guest. At the very beginning of the game, using your main account stand directly in front of the guest character and win 50 duels (melee with both controllers to start the duel, melee again with the main controller to win.) This will provide a total 166 badass ranks. You can then create another new character and repeat this process.
Minecraft Easter Egg
After Chapter 9, Go to Sanctuary Hole and jump off a cliff then and go to Caustic Caverns run northwest till you reach the Gurdian Ruins and go to the Minecarts and turn right, jump over the rectagular rocks and turn left. and yyou will find Minecraft Dirt, break though those and you will find Minecraft stone, cobblestone and coal. Break though those an there will be Creepers and blocks of gold, diamond, irridium and other surprises. Once you kill the badass creeper (yes thats really his name) you will get minecraft skins such as Steve Head and Steaves Cloths.
Enter the Konami code:up, up, down, down, left, right, left, right, B, A, Start, at the title screen to unlock Extra Wubs in the gameplay part of the options menu. Extra Wubs literally does nothing.
Challenge Accepted 30 Completed level 1 of all non-level-specific challenges with a single character
Goliath, Meet David 15 Allowed a Goliath to level up four times before killing him
Went Five Rounds 25 Completed Round 5 of any Circle of Slaughter
Not Quite Dead 5 Reached level 5
Better Than You Were 10 Reached level 10
Always Improving 25 Reached level 25
Capped Out…For Now 50 Reached level 50
Arctic Explorer 15 Discovered all named locations in Three Horns, Tundra Express, and Frostburn Canyon
Urban Explorer 15 Discovered all named locations in Sanctuary, Opportunity, and Lynchwood
Highlands Explorer 15 Discovered all named locations in The Highlands, Thousand Cuts, and Wildlife Exploitation Preserve
Blight Explorer 15 Discovered all named locations in Eridium Blight, Arid Nexus, and Sawtooth Cauldron
World Traveler 50 Discovered all named locations
Sugar Daddy 10 Tipped Moxxi $10,000
Decked Out 25 Had Purple-rated gear or better equipped in every slot
Sabre Rattler 20 Killed 100 enemies with the Sabre turret
Phased and Confused 20 Phaselocked 100 enemies
So Much Blood! 20 Gunzerked continuously for 90 seconds
Cute Loot 15 Killed a Chubby
Tribute To A Vault Hunter 15 Got an item from Michael Mamaril
Definitely An Italian Plumber 15 Killed Donkey Mong
High-Flying Hurler 10 Killed a flying enemy with a thrown Tediore weapon
Token Gesture 20 Redeemed 25 tokens
Unseen Predator 20 Remained in Zero's Deception mode for ten seconds straight
Build Buster 20 Killed a Constructor without it ever building another bot
How Do I Look? 25 Unlocked 10 customization items
Friendship Rules 10 Revived someone from "Fight for Your Life!" that is on your friends list
Better Than Money 15 Purchased 5 items from the black market
Up High, Down Low 15 Gave Claptrap a high five
Bounty Hunter 25 Completed 20 side missions
Did It All 40 Completed all side missions
Captain Scarlett and Her Pirate's Booty DLC:
Treasure Hunter 75 Complete the mission "X Marks the Spot"
Gadabout 25 Discover all named locations in Oasis and the surrounding Pirate's Booty zones
Completionist 25 Complete all Pirate's Booty side missions