Well that was dumb...

Remembered another one. Working as a truck tire mechanic and for some reason decided I was going to start chewing tobacco. Had a big old plug in my cheek, pried the lock ring off a wheel and flipped it up against my thighs to hammer the rim out. I must not have been paying attention and got my knees in the way of the rim, which shot out on the first good whack. My reflex was to swallow. I quit chewing then and there. Well, I guess I quit as soon as I finished puking and gagging.