Hi,
This suggestion stems from one of my hobbies - competitive nerf wars. Quite unlike the wimpy blasters that you get off-the-shelf, we modify our blasters to shoot harder, faster, and more accurately. An interesting project would be to build a high-tech nerf gun, decked out with such luxuries as a shot counter, a LiPo battery to power the flywheel motors, a tacticool flashlight, and laser targeting.
Live Long & Perspire,
Sebastien Bolle