One of my best was in 1968, in some redneck bar in New York State. My best buddy took me there (the legal drinking age being 18 then, and we were both 19).
So we're sitting at a table in the middle of the floor, drinking beers, and some guy comes over and asks my friend if the green Army field jacket he was wearing meant he'd served in Vietnam. No, my buddy answered. Well take it off, this guy demands, you have no business wearing it.
(The issue of Vietnam was very passionate in those days, which I doubt younger guys today would appreciate. And ironically within a year we were both in Army uniform, which that redneck bully likely never was himself.)
So my friend took his field jacket off, which kinda surprised me. Then this guy (now joined by others from the bar, surrounding us) told him to take his eyeglasses off, which my friend did, too. "Now take your pants off!" he demanded.
At that point I'd had enough, got up and simply punched him out. Total mayhem erupted, like from a Hollywood movie, chairs being thrown, everybody fighting everybody.
We fought our way to the door, got out and raced for his car, right outside at the curb. We burned rubber as guys poured onto the sidewalk swearing at us. We had a few bruises but laughed about it all the way home to northern New Jersey.
I've had lots of other fistfights, but that one I always remember.