Seeing is Believing Keychain by Himitsu Magic

"I think your card is on my keychain," says the magician.

"But I didn't select a card," exclaims the participant.

"Please select a card," says the magician.

A card is selected, and the magician's keychain is shown...it says "Your card." Hilarity and/or awkward stares ensue. "Watch," whispers the magician.

When you turn the keychain, the words morph into "8 of Heart," which matches the selection!