A wildly popular trick! This is a seemingly impromptu miracle. The magician displays a quarter, and then takes a bite out of it!
The spectators actually see teeth marks in the quarter. A piece of the coin is missing, apparently in the magician's mouth. The magician then restores the quarter in a flash - by spitting the bit-out portion of the quarter back on to the chunk remaining in his hand. In the blink of an eye, the quarter is whole again!
No sleight of hand is required. Complete with instructions that teach you how to perform this feat with a borrowed quarter!