I've got a character idea: a ventriloquist/puppeteer whose puppets contain trapped, defeated minor demons. The puppets contain the demon's former powers (under the puppeteer's control) and personality (absolutely [i]not[/i] under his control, and generally pissed off at their present situation). Useful both in combat and performance!

Basically (and I wish I could think of a better comparison), Jeff Dunham if all of his puppets had free will, magical powers, and hated him.