Frequently, both as a kid and as an adult. In school, I'd say I was assaulted on average 2 or 3 times a year. Usually it didn't last long, teachers break it up, and everyone laughs. I remember once in like 4th grade we were all in the gym, like the entire grade, they opened the gym up, retracted the divider so it was full size. I don't remember why, but everyone was there and this kid Brad (yes, lol) who was a sort of cool kid (but manlet - didn't matter at the time, I wonder how that's worked out for him as an adult) started fighting me. The gym was crowded and chaotic, so the fight went on longer than they usually do before gym teachers could separate us. It was probably just a minute, but that feels like a long time in those kinds of situations, especially when it usually gets broken up in like 10 seconds. The entire gym was chanting "Brad! Brad! Brad!" while we wrestled like pansies. I held my own and I can be proud of that.
One day in 7th grade I sperged the fuck out when this kid (either Nick or Zach, I can't keep them straight this many years later, half the forum wasn't even born yet when I was in 7th grade) who sat in front of me attacked me right in the middle of music class. I don't know what happened, but that was the fucking breaking point. I managed to push him off balance and he tripped on the chair/desk (the chairs are attached right to the desk) which kinda fell on his legs, and I jumped the fuck on him and started repeatedly driving my elbow into his nose, then jaw, then forehead, as he moved around trying to block. The music teacher was like an 80 pound washed up hippie foid, of course, and I was starting puberty, so she couldn't peel me off, I kept elbowing him until she basically rammed her entire body into me to knock me off him. Eventually some other teachers from the hall came in and I got dragged to the principals office. 1 week suspension, today I'd be expelled, no doubt. When I came back Nickzach's face was still kinda bruised and tender looking, it was beautiful. They rearranged our seats, and he never bothered me again. I was a skinny, kinda short kid, but that gave me the reputation I needed. You can be a skinny manlet, but if people know you will fight like you've got nothing to lose, they will be afraid of you anyways.
That's part of why I gymcel today. Oderint dum metuant.