Gunslinger Pro by Steve Cantwell
Four cards are shown and the spectator is asked to hold his hand out palm u. The spectator is given two cards, shown to be guns, and the magician keeps two, also shown to be guns. He explains that magicians, having the quickest hands, were the best gunfighters in the Old West. Quick as a flash his two guns change to show "BANG". He explains that he has shot the guns out of the spectator's hands. He turns the spectator's cards over to show they have changed to guns being shot out of hands (or blank cards if that is preferred)!
The Pro Effect:
At the end of the above routine, the magician offers to prove even further that the guns were shot out of the spectator's hands and asks the spectator to turn them over. The spectator (and everybody else) is astounded to find realistic prosthetic bullet wounds on the backs of his very own hands!