many, many times.
i was playing with a paperclip and it ended threw the side of my thumb.
then back in the days when those little skateboards, tech decks, were cool in grade school, my class would sometimes use a pen or pencil to do some of the "tricks" if we didn't have one with us, and thats how i got a pencil to go completely threw my hand, which is still the most painful thing to ever happen to me.
and then there was the first time i ever drew a katana, i put my thumb in the wrong place and as i drew the blade is ever so lightly slide across my thumb, i wasn't aware that i had cut myself till i went to chance the channel on the TV and flexed my thumb and it felt odd, so i looked at my thumb and saw blood, and then moved my thumb and saw the cut split open. it took me a minute to figure out what happened.