Duplicating Weapons, Money and Items
- Start a co-op game with at least one other player. Stand next to another player, and initiate a trade. Give them the desired weapons/items/money you would like to duplicate. Then, immediately quit the game without saving by exiting to the Xbox dashboard using the Xbox Guide button. Since the game did not save after you traded the weapons/items/money, you will still have them, and the other player you traded them to will also have them. The other player can then give you weapons/items/money while using the same method. Repeat this as many times as desired. Note: Do not trade items near an auto save point to prevent the game from accidentally saving while trading the items.
-In Three Horns Valley, go to the hideout where you fight the Bad Maw boss. Kill him, and pick up the Eridium he drops. Then, enter the Bloodshot Stronghold, and choose the "Save and Quit" option. Continue the game, return to Three Horns Valley, and kill Bad Maw again to get more Eridium. Repeat this as many times as desired
Better weapons and items
-Go to any slot machine after the game has recently been auto saved. Play the slot machine as many times as desired. If you do not like the weapons and/or items you won, simply quit the game without saving by exiting to the Xbox dashboard using the Xbox Guide button. Then, continue your saved game to still have all the money you spent on slot machine. Repeat this process as many times as desired to get better weapons and items.
Easy "Sugar Daddy" achievement
-Once you have $10,000 or more, go to Moxxi at the bar in Sanctuary. Put $10,000 in her tip jar to get the "Sugar Daddy" achievement. Then, quit the game without saving by exiting to the Xbox dashboard using the Xbox Guide button. When you continue your saved game, you will still have all the money you tipped Moxxi.