Wizard’s Hat of Conjuration

Default Bonus: 
Mental defense: +1 MD (adventurer); +2 MD (champion); +3 MD (epic).

Once per day, you can pull a useful non-magical common item out of this hat. The item must be able to fit through the brim of the hat, so you couldn’t pull out a siege engine or a horse. You could, though, produce a sword, or length of chain, or a saw, or a delicate vase decorated with salacious paintings of frolicking kobolds. The hat can also produce small living creatures, like rabbits or cats or doves or maybe even the aforementioned frolicking kobolds.

Kleptomania; you unconsciously steal items and stick them inside your hat. Sometimes, you can’t find them again afterwards.