I've had a couple of close calls..
And I've seen two punter classics.
Once with a bunch fooling around in the range area - twerp points it at his mates groin and says something like 'can you image how much it would hurt?', at which point the thing goes off, at about 2 feet range. Clever.
Another one where a marshal was watching the last throes of a game and an overexcited girl cut lose at a run-by and got the marshal standing just near her.
Amusing thing is, in both cases there were no howls, no writhing, no histrionics at all. It just looked like their bones had turned to jelly and they sort of slowly melted to the ground and lay there clutching the wound for about five minutes. Looked very nasty indeed. I don't wear a cup when playing (baggy trousers instead) but you'd have to be insane to marshal without protection.