Take two quarters.  Show the sucker one of the quarters and put it under a beer bottle.  Tell them that you can remove the quarter from underneath the bottle without touching the bottle. You then, with the other quarter hidden in your hand, reach under the table or the bar and smack the underside. Remove your hand and place the hidden quarter on the table.  If you do it right (meaning make it look hokey) they will say na-ah you had another quarter in your hand and you say no the quarter is gone, take a look, at which point THEY lift up the beer bottle and you remove the quarter still underneath.  The quarter was indeed removed without YOU touching the bottle.