Deck In Knuckles

The magician puts the deck in his knuckles and asks the spectator to hit the deck, after a few hits of the deck, only one card remains between the magician's knuckles, the spectator's card.

All you need to do is get the spectators card to the bottom of the deck, the rest is self working. With the selected card on bottom, hold the deck face down between the knuckles of your pointer and middle finger. Ask the spectator to hit the deck; the spectator will likely the deck not knocking any cards out. Tell the spectator to hit harder. You have some control over how many cards fall out of the deck with how hard you are squeezing it. Have the spectator continue to hit the deck until only one card remains, which will be the spectator's card.