Wayne Houchin - Indecent
Here's what your spectator sees: a card is selected from any deck. It's a free choice-- no force. Signed. The card is then lost in the deck, then shuffled. The cards are then dribbled on top of a sealed Ziploc bag.
Slowly, the bag is lifted up from underneath the chaos of cards to show that one card is sealed INSIDE the bag-- the spectator's signed card.
Credit note: Inspired by an effect by Anthony Miller.