Well, not me personally, but the other guys in the band did.
The guitar player, who has anger issues, had too much to drink and started turning up his amp. Finally he got too loud and the drummer complained that he couldn't hear vocals or anything but guitar. The drummer was getting pissed off about the guitar player.
After we stopped playing the drummer was telling me how loud the guitar player was and the guitar player started yelling obscenities and pushed the drummer in the back. This turned into a fist fight, but people dragged them away to separate them.
Of course, all this happened on stage in front of all the people.
Yikes! How embarrassing ...........