In college I found this deck of cards where all 52 cards were a 6 of clubs. That night we were having a party, so beforehand I hid a few cards in random places around the house... behind a picture, in a drawer etc... Then when things were in full swing I had a girl select a card, look at it, and place it back in the deck, then I would tell her to look behind the picture... it brought the house down. They were amazed and even though I ran the same trick 3 or 4 times they never caught on that it was a 6 of clubs every single time.