You take out a deck of playing cards which are shuffled, and they ARE shuffled by you or your spectator. Any card can be selected (no force) and the card can even be signed if you want. You then take out a small light bulb and screw it into the middle of the card case. The card is lost in the deck and you place the card case on the table. You then take a card from the top of the deck and move it over the light bulb, nothing happens so you place this card aside. You do this again, one card at a time until suddenly the light bulb lights up on ONE card. You can show that this doesn’t happen with any other card. Only one will make the light bulb light up, the spectator’s card. You can then hand everything out for examination.