Here's a version I published in Genii --
BRAIN TO WALLET
EFFECT: A card merely thought of appears in the magician's wallet.
METHOD: No sleights. No moves.
You need a deck of cards, a Sharpie and a hip-pocket wallet. The wallet has six bills in it.
Start with the wallet and the pen on the table.
After the spectator shuffles the cards, have him deal two hands of poker. He chooses one of the hands. You take the deck and add the other hand to the top.
Say that this a game of mental poker. Have the spectator think of any card in his hand. He then mixes the cards face down so that even he does not know the location of the thought card.
Place the five cards face down on top of the deck and false shuffle retaining them there.
Still holding the deck, pick up the wallet, open it and remove a bill. Hand the bill to the spectator, along with the pen.
As you say that somewhere in the deck is the thought card, spread off five cards, obtain a break below them, then square them back on the deck, maintaining the break.
Ask the spectator to write the name of his thought card on the bill and then fold the bill. The rationale: you want to keep him honest in the game that follows and you want to ensure that he doesn't forget his card.
Turn your back to him as he does the writing.
Once you turn, shove the five card packet into the wallet. Keep the wallet closed and use your right thumb as a guide. You can stick your thumb into the wallet prying it apart far enough to allow a smooth insertion of the five cards.
Turn around when the spectator finishes. Drop the deck on the table. Open the wallet and pretend to count the bills, glimpsing the face of the first card in the packet as you do so.
Tip the wallet up and back slightly, so only you can see its interior.
Tell the spectator that you have only got five bills left. You are going to try and guess his
card, one bill for each guess. If you don't guess it before you run out of money, all the money on the table is his.
Guess the card you just glimpsed. If you're right, pick up your money and then offer a side bet (more about the side bet later).
If you guessed wrong, dig into your wallet and move the first card out of the way by sliding it to the other end of the wallet. Glimpse the new card on the face of the packet. Remove the next bill and guess again.
There is no need to hide the action of sliding the card to the other end of the wallet since from the spectator's point of view it looks as if you are simply separating a bill before removing it.
Continue this process until your guess is right.
Drop the wallet on the table. Offer a double or nothing bet. Hand the deck to the spectator and have him shuffle it then place it on the table.
Bet the spectator that even though he has thoroughly shuffled the deck, you know the exact location of his card.
It could fifteen cards from the top, or twenty-five cards, but you know exactly where it is.
Once he accepts the bet, pick up the wallet and remove the thought card. Pocket the wallet. You can add the four other cards back to the deck later.