You can earn unlimited items if you open a chest that contains multiple items, leave at least one behind, and then fast travel to another location. This will work with chests that contain Amulets of Power and other items, as well, which lets you gain unlimited skill points.
One place you can do this is in Crestwood. If you have a Rogue with you and have the “Deft Hands, Fine Tools” perk (unlocked after four others in the Secrets tree), you can open a locked door to the right of the Crestwood fast travel location, and find a chest with an Amulet of Power and a Gold Amulet. Take the Amulet of Power, leave the Gold Amulet, and fast travel to another location. You can then return to get another Amulet of Power.
This may be patched out of the game.