In 1st grade ( I think it was 1st grade ) the first day of school, it was our lunch period, and I was waiting in the lunch line and some kid cut in front of me. Punched him in the balls. I got 3 days detention on the first day of school and my parents were pissed at me.
In 6th grade I got in a fight with one of the more muscular guys in the school, not because he wasn't friends with me, but because he saw me holding a kid by his neck. I was holding the kid by his neck because he twisted my head when he was behind me for some stupid reason. Instead of trying to explain to the muscular kid why I was holding him like that, I decided to fight him and got the shit beaten out of me.
In 8th grade, there was this annoying short pair of twins that would constantly pick on me. they had the most annoying laugh and buck teeth I've ever seen, and just the sight of them made me hate them. They would always make fun of me, and one day I had enough of it. One of the twins kept... fake hitting me? I don't know what to call it. He would keep throwing his fist at my face and stopping before he hit me just so that he could get me to flinch, and after the 4th time I pushed him as hard as I could. There was a steel fold-up chair right behind him. He tripped over it and he hit his head on the concrete floor. Luckily for me the teacher didn't do anything to me because he knew the kid was being a jerk to me for the longest time.
Thankfully in high school I haven't done anything too dumb that I know of. Haven't gotten in any violent situations since that last one.