Dungeon Hunter: Alliance

This trophy is best earned while playing on Legend. To unlock this trophy one of your characters must be holding over 1,000,000 gold on him at one point. Some players claim to have unlock this trophy naturally by maxing out their rouges Treasure Finder skill and equipping Magic Find armor while playing Legend from start to finish. However, chances are that most players will finish the game with around 600-750k on average and will have to grind out the remaining gold by killing the final boss: The Dark Queen/Dark Fairy over and over again. Every time you kill her you get to collect her loot and the loot from the two treasure chests that spawn after she's dead. Collecting this loot altogether will add up to about 25.5k worth of gold every time you sell them to merchants. And since you're maxed out in level with some of the game's best gear at your disposal she'll be a cakewalk every time for it only takes 1-2 minutes to kill her, which isn't bad at all. Grinding her can take about 2-3 hours of your time due to the games long loading times, visiting potion dispensers for more potions, and visiting merchants to sell your loot that you farmed.

There's also a multiplayer Item Duplication trick for online use only that's very similar to Borderlands own item duplication trick that can be found here. Thanks to OWTLAW274 for making this discovery.