This sleek paper model jet airplane, perched on the point of a pin, is a perfect desktop toy. Give it a gentle shove and it goes into action - dipping, revolving, but never once loses its balance. The secret behind this amazing feat is a penny glued to the underside of each wing. With these coin counterweights in place, the plane's center of gravity is located precisely at the tip of its tail.

As an alternative, you can suspend the jet from a thread passed through the balancing point. Hang it from your ceiling, or attach it to a hook so that you can suspend it from the edge of your desk.