I made an off-key remark about his hair colour after he told me to "fuck off" because I'd haphazardly pointed out that the reason that he wasnt getting any signal was that he'd forgot to turn the gain up. Go figure. Not the most professional of me it must be said but if someone sees fit to give me no respect then I'm not gonna be rolling over to give them some.
I wasnt even paying attention and he came round and threw a punch at me from behind when I wasnt looking, caught me in the back of the head, the sort of punch from someone who has never been in a serious fight before but just caught sand in his vagina one day and decided if he was going to snap I was the one to do it with. Of course I got up and had the default reaction to just grab him, but just as I was getting in his grill this big bruiser of a guy who was in the band we were supposed to be working with got there before me and told him to basically get the fuck out, he mysteriously disappeared for the rest of the day, leaving me to apologise to the band about the unprofessionalism of the situation.
Next time I saw the guy I basically got him in private and told him if he had a grievance with me he should air it in private and if something ever happened like that again I wouldn't stop short of laying him flat; he quickly saw fit to apologise profusely.