Borderlands 2 Tundra Express Secret/Developer Chest Farm
There is a developers chest in Tundra Express a short distance from the fast travel station at the base of a cliff. It can spawn some good loot/mods which can help if you are having problems getting past Wilhelm. Also, if you have an over powered character, this chest is useful for picking up high dollar gear to transfer to lower level characters for them to sell for quick/easy cash.