School-Sanctioned Egg Chucking
In sixth grade, I had an interesting science teacher. After our late-year lesson on simple machines - levers, pulleys, screws, etc. - we were offered a challenge: Create a device that used a simple machine in some fashion to launch an egg as far as you possibly can. The boy and girl that flung their eggs the farthest would be treated to a nice dinner out with the teacher.
The game was on! I came up with a few crazy designs on paper, but basically stuck to the same principle - using compressed air. Yeah, ok, not much of a simple machine, but in the end there wasn’t much to the device beyond a simple lever.