Lighter than air!
This one has to be seen to be believed!
Let your spectator cut to a card in the deck.
You can even use just part of the cards, if you'd like to make this easier to handle.
Place the chosen card on top of the deck-
and suddenly it floats AWAY from the rest of the deck!
At your command, the card returns to rest on the top of the deck.
And YES, you can instantly make the card float away again!