Mine was a ND, Negligent Discharge. This was just pure stupidity on my part.
I was about 17 and deer hunting in Vermont. Let's just say I was not a overly excited about being there because I am not a fan of hunting (I don't have a problem with people that hunt, it's just not for me). Anyway, I was sitting in a clearing with my .30-06 across my lap, bored off my a$$, and I started playing with the safety. The safety was right behind the trigger just outside the guard. Click, click. Click, click. Click, click. Click, BOOM! Needless to say it scared the crap out of me and I haven't been deer hunting since. Haven't had an ND since either though.