I've been blessed with the opportunities to fire all kinds of neat stuff. Whilst in the military I did my level best to qualify on everything in inventory that could be carried and fired by 3 folks or less. That is a lot of stuff.
I built really stupid stuff as a kid, and am grateful I didn't kill myself or hurt anyone. The best one of those was a match head rocket made from a wrapping paper tube and two boxes of aluminum foil, and 5 boxes of matchbooks. Friend Kurt an I spent one entire saturday chopping the heads off the matchbooks with a hatchet, cinderblock, and hammer. I still giggle over watching that thing go. It really worked, just not like we planned. We did manage to put the fire out before any real damage occured.
But the oddest weapon was a 12 gauge a friend of mine built out of black iron pipe, a threaded pipe clamp, a nail, a door hinge, screen door spring, a piece of german siding whittled down with a swiss army knife for a stock, with the reciver/barrel assembly attatched with hose clamps.
He fired it once,
I fired it once, pronounced it a really very very bad idea.
He fired it a couple of more times before the threads on the cap gave up, the cap hit him in the forehead requiring 14 stitches. We were 13.
"He got the cut falling down in the woods and hitting his head on a rock" That was our story, and we stuck to it. Now only you know!