Never have been myself, but I watched a big mouthy foreman crank an old Wisconsin engine on a welder and knock himself out. He made fun of all of us for not getting it started, then told us to step back and he'd show us how to crank it. It was about 10 degrees that morning - he bent over, stuck the crank in and whipped it over real good, but he was pulling the crank out as he cranked. When it came loose from the engine, the end spun around and hit him right on the chin. He went down like a big oak tree, and just laid there. Didn't even quiver. I'm ashamed to say that we couldn't even check on him because we were laughing so hard. We got him by the heels and drug him over by the fire barrel, and he finally came to. Every morning after that we'd holler for him to come show us how to start that old welder and he'd get red as a beet.
I watched the same guy lop a finger off one morning too, but that's another long story. . .
He was a dangerous man.