A pistol that can shoot NERF(TM) foam darts (amongst other things). Needs nothing other than some filament, 3 printed bits, 2 rubber bands and a foam dart.
It seems to generate more power than yer average foam dart gun, because I'm not bound by children's toys regulations. So, test it before using it in combat games.
It's parametric so you can change the grip size, dart dimensions and all sorts of stuff. No sights yet, and it could do with some clip on fancy grips, so hack away :)
Print. Knock the follower forward into the barrel and move it around a bit to clear fluff. Ream out any clogged pivot holes to 3mm. Use 2 short lengths of 3mm filament for the sear and trigger pivot points. Tuck a longer length of filament in the hole at the front of the handle until it pokes out the back. This is a spring to hold the sear in the "up" position. Melt filament pieces into place. DO NOT melt the spring to the sear. Fit two rubber bands, pull follower to the rear until it engages firmly with the sear. Poke a dart down the barrel, aim at something that doesn't care and squeeze the trigger firmly.
If you do not have 3mm filament, here are printable pins and springs http://www.thingiverse.com/thing:43551
Assembly video here: