Borderlands 2 Easter eggs

Hidden Chest
In the Vault of the Warrior, hidden chest can be found right by the lava:

1) walk until you see a Metal Bridge inside the cave, stop by the lava stream about 10 feet before the bridge
2) Look down, there should be step-stone liked rocks by the edge
3) Jump onto the lava towards the left wall, now you should able to see the hidden den.

updated: check out the latest Borderlands 2 Neoseeker Video Walkthrough section or here for this cheat