Total Rip trick
A spectator's borrowed quarter is held at the magician's fingertips. The spectators are asked to watch the coin and not let it out of their sight. The performer begins rubbing part of the coin to "soften the metal" and with the coin clearly in view, he reaches over and rips down a piece of the coin, bending it back! The bizarre-looking coin is then immediately handed out for examination and the spectator's can't bend the coin!
Comes complete with the very special coin and fully photo-illustrated instructions.