Oh, I'm good at this;
1. The guys that doesn't bother bringing all the stuff they're gonna need. I mean, 3 bands, a bass player and 2 guitarists each, and I'm the only one that thought of bringing a tuner with a cord?
2. The sound guys that has to use crappy inline DI's instead of either my Sansamp or the one in my amp. Even if I can give them any kind of mix they want, post/pre EQ, straight out of the Sansamp or what. Nono, they have to use their old beaten up DI that crackles like crazy.
3. Sound guys or other bands that doesn't know **** about gear at all. ("Hey man, you can't coil your cables like that, they'll go bad, you need to use Magic tape like me so they don't get snagged, trust me, I've been doing this for decades!" Well, I can use a soldering iron to fix my cables if they get snagged, and just because you can't tie a 30 foot cord into a bundle fast without braking it or damaging the conductors doesn't mean my cables have to be sticky from all that tape. And oh, my cables last a decade or more, might it be you're just using bad cables?)
4. People expecting to borrow your rig just because it's the biggest at the gig? No, if you can't even bother listening to me when I explain how you get the gain right on the pre-amp, then the leads for the rig is coming right down from the stage with me.
5. People telling me that if my Fender isn't Made in the US of A then the intonation can't be right and it's gonna sound like crap and I need to get real or go home. Well, guess what, I play instruments that sound good and play great, then care about how much it's price boosts my ego. On top of that the bloody ****** had the nerve to go give my friend a beating over some really dumb stuff the same evening, I mean, who the **** kicks somebody repeated times in the face when they're laying down? My friend is now in such a bad shape that it pulls to the right when he tries to walk in a straight, along with multiple stitches in his face. I wish I had beaten the **** out of the guy then and there, I was stone cold sober and pissed off, he was piss-faced drunk and offering me a beer bottle which would have done well as an ad hoc weapon.
About the dress-code stuff. I don't care what you're trying to pull off in that department, but if you don't pull it off, then sorry but you just look like an idiot. Goes for the whole showmanship as well.