Hmm, the dumbest stuff I've done? Back in Scouts, when I was a Tenderfoot, I was kneeling with both knees on the ground and using a hatchet, missed the wood and nicked my knee, jabbing a corner of the blade in, so there's a 3/8" scar above the outside of the kneecap. Then a few campouts later, I had my skillet on the fire,knelt on one knee, took the pan off to add more logs without knocking soot and ashes into it, resting my arm on my leg and brushed the pan against the inside of my other knee, burning myself and raising a blister about 1" across.
Another dumb thing I did was sharpening my pocketknife on a ceramic V-stick set, around that same time (early in Scouts), and when I made the downward motion toward the left side, I missed the end of the rod and landed the tip of my very sharp knife into the top of my left wrist, holding the base! I said, "OK it's sharp enough now!"
For as many times as I cut myself back then, it's amazing they didn't kick me out as a danger to myself, or at least take away my "Totin' Chip" card.
Matt in Texas