So there you are hanging out in a pool hall or a pub, when someone wants to see something amazing. Never the type to disappoint, you have them select and sign a card. Then they shuffle it back into the deck.
With no idea where the card is, casually you walk over to the dart board, with the shuffled deck in one hand and a dart in the other. The cards are tossed into the air. The dart is thrown through the cards were it sticks into the dart board, with a little something special... their signed card!