A FIRST OF ITS KIND, IMPOSSIBLY LINK A BORROWED FINGER RING ONTO A SIGNED HOLE PUNCHED CARD
Your spectator chooses a playing card. You hand them a marker and have them sign their name right across it. You take out a hole punch and make two holes in one end of the card. You then borrow their finger ring and IMPOSSIBLY LINK THE RING THROUGH THE TWO PUNCHED HOLES!
YOU THEN HAND THEM THE CARD WITH THEIR RING STILL LINKED ONTO IT! IT IS REALLY ON THERE - IT'S JUST IMPOSSIBLE BUT THEIR OWN FINGER RING REALLY IS LINKED ON TO THEIR SIGNED CARD!
You finish by giving them back the ring in the only way you can - by tearing it back off the card which they may now keep as a souvenir.