A Christmas gift that I received from my lovely wife is a kinetic creature. This is a cardboard model animal — mine is an elephant named Elly — that through clever design can walk. The walking mechanism is based on a simple crank shaft paired with cleverly designed legs that act as linkages. Here’s a slide show of the construction and a video of it in action:
One exciting thing about this toy is that you can replace the hand crank with a motor. They sell a kit for this but I plan to make my own.