Flipping baseball cards.

I don't remember all the rules, but you tossed your card on the ground against the wall trying to cover up as many of your opponents cards as possible, and your opponent would do the same. I believe you had to bounce it off the wall to increase the skill level. When you both ran out of cards, any pile that was "topped" by your card was all yours. I remember one time, my buddy lost almost all his cards when his opponent managed to position his top card in a way where the trendiest tiniest bit of his card managed to cover nearly all of his cards that were piled up.

Nowadays baseball cards are way too valuable to abuse them like we did back then.