You're able to read a spectator's mind. A spectator shuffles a deck of cards and memorizes the card at the bottom of the deck. So you can't see the selected card, the deck is slipped back into its box. After a bit of mumbo-jumbo, psycho-babble, you're able to tell the spectator the exact card that he is thinking of.
Beforehand, you've cut a hole in the card box. When the deck is placed back into its box, you can see the chosen card through the hole. Yes, you'll have to wreck a card box, but the trick will be worth it.