Here is a David Blaine Secret for you! On one of David Blaines magic shows on TV he has a card selected and signed. The card is put back in the pack by the spectator and David shuffles it. He appears to have problems locating it and keeps picking the wrong card over and over. Finally he starts coughing and seems to have regurgitateed the spectators card, tightly folded with the spectators signature!
How the magic trick is performed

Have a spectator to pick a card, sign it and show it to the audience, and place it back in the deck. Use any perfered method to move the card to the top of the deck (unoticed of course). Then holding the deck in a standard dealing position, get a finger break under the top card (which should be their card now) and palm it with your right hand.

Now perform a cut or a quick shuffle and give the deck (minus the card you have palmed) back to the spectator to shuffle it even more. Now for a good misdirect, turn your back to the spectator and tell them its so you dont see what they are doing. While turned away, fold their card and put it in your mouth. You may have to fold it up into eights or less and put it between your cheek and gum. Now turn back around and face the spectators.You should be able to talk normally.

Take the deck and act like your messing up trying to reveal the card. This is where you can really put on a show. Act sincere and make it appear like a real messup. You can now start to do whatever you want to get the card out of the mouth, you can act like your coughing and gag it up or act as if you ar e hurt and "something" inside you wants to get out (kind of like the alien movie). Then spit out the card infront of them. Unfold the card and show them its the signed card.