I've done Judo when I was a kid, and I was in the University MMA club for a while.
I've been attacked once by a group of guys while I was on my way to get dinner from work.
One of them balled up a magazine and threw it at me and said "Here, have a magazine ****!"
I turned around and called him a shithead, there were 5 of them, all with beer bottles in their hands and little plastic Australian flags hanging out their pockets (it was the Australia Day long weekend), he tried to get in my face, and when I told him to piss off and turned away to look across the road to see if it was safe to cross he punched me in the side of the head. I just looked at him and said something along the lines of "go home and have a lie down or a nap champ". One of the other guys stepped in to hold him back, and one of the other guys stepped in and asked me "what did you just call my friend?" I told him that I had called his mate a shithead, and why, and then that guy waited until I looked away to face across the road and popped me in the side of the head.
By now I decided to face up to them because it was getting fairly obvious that no amount of passive behaviour on my part was going to prevent an incident. The guy tried to shirt front me, and I pushed him away, ripping my shirt to shit in the process. Then he tried to shoot in for a takedown/tackle sort of thing, but he was shit and his body position was too high, so I hip tossed him to the ground and landed on top of him in a sort of side control position (for anyone who watches MMA or does Ju Jitsu). I popped him with about three left hands before I realised "shit, this guy still has 4 mates standing up around me who are all holding beer bottles, and the back of my head is completely exposed", so I completely dropped my weight, covered up and waited for it all to get broken up.
I went back to work, shirt ripped to shit, then went marching down the street with two of the bouncers looking for the guys, unfortunately we didn't find them, but if we had their shit would have gotten fucked up.