Poke a long nail into the smaller end of a cork, then push identical forks into either side. Now try to balance the contraption by resting the nail on the rim of an ordinary drinking glass.
Why It Works
You might think the contraption would be so heavy that it would tip over. But the forks' handles direct much of the weight back toward the glass. That's because the contraption's center of gravity -- where most of its weight is concentrated -- is actually where the nail meets the rim of the glass.