Bill from a Bottle Trick
Challenge a guest / friend to remove a bill from under a bottle that has been placed, upside down, on top of it. The catch is that they cannot touch the bottle at any time. Whoever can accomplish this gets to keep the bill.
Place a pen or pencil at one end of the bill and begin to roll the bill around the pen/pencil. Roll the pen/pencil towards the bottle while rolling up the bill with it. The pen/pencil will eventually begin to push the bottle out of the way. Be careful and you'll be able to push the bottle completely off the bill.