In my limited experience:
Singers: "Hang on, there's no need to panic. Stop having a screaming fit and calm down. Wipe your eyes and catch your breath for a moment. There. That's better. No, I can't hear you when you start whining like that. Are you ready to settle down? Okay, where was the last place you remember seeing your mirror?"
Keyboards: Sometimes, I think they love to change keys without warning just to watch the bassist sprain his brain. You realize that there is a point where experimenting with music theory becomes an impediment to playing "Louie Louie", right? Also, nobody is perfectly on pitch, so stop telling the guitarist to re-tune between every song.
Guitars: For all of the posturing, grimacing during solos, and frenzied berserker playing style, some are surprisingly girly when they break a nail. In addition, their version of "helping" during the load-in/load-out process consists of carrying their own amp. There are notable exceptions, of course. Some ask you to carry in their amp for them.
Bassists: "Dude, I'm not kidding, the front of the stage is that way. It's where it has been all night. No, that's a fire escape. Yes, I'm sure. I know the guitarist is re-tuning again. He listened to the keyboardist. Yes, your speaker cabinet is bigger than his. What do you mean, 'How does the next song go?'"
Drummers: I sit in the back. I don't dance around the stage. I don't pose for the fans. I don't toss my silken locks over my shoulder. Granted, that may be because I don't have silken locks anymore, but you get the point. Also, I can't dance. Anyway, I'm working here. Yes, I got here hours before the rest of you to haul all of your gear and I'll be here long after you've all gone. I'm the one who helps everybody remember what song is next. When you lose your place and you can't remember what verse we're on, I'm the one who will guide you home. I'll give you a drum fill to clue you in when it's time for your solo. Yes, after the show, you'll greet fans while I catch my breath, wring the sweat out of my shirt and start tearing down the gear. It's okay, though. Most people want to keep a certain minimum safe distance from a drummer out of a sense of self-preservation. You can't blame them for having standards. Hang on. Watch me now. I'm making eye contact with you and giving you a big drum break. That's right. It's time for your solo.
Audio Engineer: I work with morons. Not the clever, creative, or cute morons, mind you. No. (sigh) "Your vocal is already up in your monitor, the reason you can't hear yourself is because you're holding the mic two feet away from your mouth." "Oh no. Don't you glare at me because you played the wrong chord. Maybe if you showed up for a rehearsal once in a while you'd know how to play the songs." I used to have dreams, you know. I wanted to work in a nice studio with great musicians and be a part of making some audio magic. Instead, I'm running sound for a band that shouldn't be allowed to play for the Grand Opening of a 7-11. (sigh) "Yes, I turned up your guitar for your solo. You rock, dude." If that monkey on the drums keeps smashing that crash cymbal like that I'm going to shove it down his throat. My head is pounding. I don't know how much longer I can keep doing this. (sigh) It's only been 10 minutes. Did that bassist just fall off the stage? Maybe it's not too late to go back to filing papers at the insurance agency. Oh, good. the drummer found his cowbell. That will be the next thing I cram down his gullet. I work with morons.
jk :)