Yesterday someone was shooting their Ruger .22 pistol and was in an awkard position shooting with their right hand from behind a barrier to the left.  Well I used my they used their left hand to steady things up a bit and wasn't paying attention to where their thumb was.  

Anyway it removed about an 1/8 of an inch of their left thumb nail all the way to the meat in a neat little triangel design.  The tip of the slide caught it.  The guy said it hurt too...... I wouldn't know

This dude shoots all the time, always uses the upmost care in being safe, but was so focused on the target he got careless and paid a samll but painful price.  He will be ok, the pistol is ok, and the target was terminated.

I am sure that he isn't the only one this had happend too, cause I can feel my thumb hurt just talking about it

Yeah, it's happened to me before.  Not the thumbnail thing, thank christ, but I was dumb enough to have my thumb raised up right behind the slide (I can't remember which one, actually) as I fired.  The thumb and part of my hand got nice and numb.

Didn't even know it was bleeding until I noticed there was blood all over the steering wheel half-way to my house.

I also know a guy that did the same thing, but rather the thumb nail it was the flesh part.  Boy did it hurt, err, boy it looked like it hurt.