Draw Penrose's Triangle
Draw a perfect triangle on a piece of paper. Extend the lines beyond each corner by the same amount on each side. Add extensions at 45 degrees on each line and draw until they are longer than the original length of the triangle. Turn another 45 degrees and extend the line on each side until you are back to the starting point. Do not extend the lines beyond the triangle. Close the gaps by drawing a short line in each and you have created the "Impossible Triangle."
Gospel Paper Tear
Take a piece of paper and fold down from one top corner, giving you a triangle at the top. Do the same for the other top corner, making another triangle. Fold the paper in half lengthwise twice. Tear the paper in half lengthwise, starting at the bottom. Unfold and separate all of the pieces of paper. One piece is a cross and the other pieces spell "Hell."
Coin Square
Take a square piece of paper and in the center trace around a penny. Challenge your friends to pass a nickel through the hole. When they cannot, fold the paper in half and insert the coin. Bend the open ends of the paper towards one another and the coin will fall through the paper.
Tearing Paper
Hand a piece of paper to a friend and offer a challenge: If they can rip the square into four equal pieces, offer him a quarter. When he finishes and proves he has met the challenge, pick up one of the pieces and hand your friend his well-earned prize.