Keep Your Balance (aka Magic Spoon)

Magic Spoon (Keep Your Balance) is a simple physics demonstration of torque and lever arms.

Have one person stand on one leg with there arms out. Another person will then try to push gently with a spoon (or just their hand). Pushing close to there shoulder is not very effective, but pushing on their hand or arm causes them to much more quickly lose their balance. The demonstrator then explains the concepts of torque and lever arms.