This is somehow really silly, but I have to admire them for the ingenuity. Some person has actually programmed an NXT to behave like an Etch-A-Sketch. Not sure how the shaking to clear works, but it is certainly an interesting use for it.
I might build one myself for the giggle of it. It has set me wandering if I could build some games - use two motors to power a self-centring, force feedback joystick, and then have some silly graphics on the screen. I might start with a worm-eating-pills sort of game.