Holy moley! Pneumatic mouth cannon!
I don't know how much more random fun you can find. I discovered this while at a buffet with my girlfriend and her brother on his birthday. Anyway, I was finished after two plates and a salad, and was balling the straw wrapper between my fingers. A tiny piece, probably a half-inch by a half-inch, ripped off in my hands. Staring at this little fragment, I put down the rest of the wrapper. I balled up the fragment, and put it between my fingers in such a manner that when I blew, it sent the fragment flying at great velocity. Thank God no one noticed or was killed. I have yet to chronograph this little amazing scientific breakthrough, but I estimate about 25 fps. Cool, huh? Anyway, rip off a tiny corner of a napkin or straw wrapper. Ball it up. Touch your thumb and index fingers on both hands together like you're rubbing something off of them. Put the tips of them together, and there should be a little diamond-ish hole between the four fingers. That's where the ball of paper goes. Put the ball in that hole, and pinch gently. Put your lips up to the hole, and blow. If nothing comes out, good! Blow to ready this little weapon, and release the pinch of your fingers to fire.