A coworker bought a small Lego kit (8290) and built the prescribed model, in this case a forklift truck.
I looked at the model, and figured I could build something more interesting with the same parts.
There's a lot of physics going on in there.
Oh, and if you like that sort of thing and are in the bay area, don't forget to visit the Maker Faire this weekend. I'll be there Saturday with my Etch A Sketch.