OK, here's the first nightmare gig that popped into my head. Few years back, fair ground gig. It had been raining long enough to turn the track between the stage and grandstands into a mud bog, truck got sideways on the in, mud all over everything, one of "those days". Headliner is an up and coming Nashville act. Female front, decent but not especially strong. Guitarist is well known in that circle. He has an old Twin that has had many mods to get "his" sound, including no master volume. You see this coming, right? Sure enough, all I hear for the first three songs is audience commentary, they're being so helpful letting me know that they can't hear the vocal. I'm quite aware of this, but smile and nod, "we're working on that, thanks!", for as long as I can take. At some point, right about the time someone hands me my first meal of the day, the complaints are getting serious as well they should, because all I'm getting in the star vox channel is guitar with some vocal in it. So I leave FOH, walk across the mud bog to the stage. I get gtr's attention, make the universal hand and body motions pleading for him to turn down. He gives me the evil glare and shakes his head slowly and all menacing, like there's no way he's going to turn down and sacrifice his tone. At this point I did the most unprofessional thing I think I have done in my career. I tell my monitor guy, "hold my blooming onion" and shove him out of the way. Grab the knob for gtr in his mix and peg that mo'f'er. Definitely have his attention now. We have a rather heated pantomined discussion about turning stuff down, he is NOT going to give in. I'm boiling by this point, my blooming onion is getting cold, I have no desire to go back to FOH and listen to 90 minutes of complaints to say nothing about a bad mix, so I leave the stage and go directly to the backstage area where artist management is hanging out. I grab the guy, "come with me", and walk him out to the house and ask him what he thinks. He immediately says there's too much guitar. No shit. I show him the gtr channel is off, cue up the star vox, and slam the cans on his head. Eyes get really wide, mouth drops, "wow". We leave FOH unattended again and go back across the mud bog to stage right where we can hear to have a conversation. I find out that this is a hired gun gtr and this is their first stop with him. After explaining what had transpired, it's also his last. Fired.
As a post script, we were having dinner with a well known Nashville act's BE a few years later and this story came up. The BE says, "that sounds like (guy's name), nobody will work with him anymore". I got the feeling this was a guy on his way down, working with an up and comer instead of the name acts he was used to at the time. And "hold my blooming onion" became one of those catch-phrases among the crew.