1. DPS standing in stuff. Yes this is definitely top of the irritating list. It makes me look bad when you die, even if you decide to stand in corrupted water because the red flashing light that signals imminent death doesn't snap you out of your tunnel vision.
2. Actually dying. If it's my fault, fine...it still sucks, but don't do that. You have cool downs, take the 1 second it takes to use it. 2 seconds if you're a clicker and you forgot what spot you put it in since the last time you used it, it was an accident.
3. Tanks that pull more than they can handle. Bro, next time you pull an entire dungeon, don't. But if you have to, a simple "watch this" will suffice. That will let your healer know that instead of sipping on coffee wondering if Darryl will be okay on The Walking Dead he has to actually pay attention. Also use cool downs, it makes my heart attack less severe.
4. Hi I'm a warrior/DK who doesn't have worry about mana and I'll be your tank tonight. Please keep all mana biscuits inside your bags at all times since I will never ever let you use them.
5. Healing the last fight in the Brewery with dps who don't want to focus the adds and have abysmal damage output. Is your dps that bad that you don't notice the bosses health at 100% for the past five minutes you've been whacking it?
6. "HEAL ME!!!" - No, I'm here to watch...
7. I've covered tanks that pull an entire room. Now don't get me wrong, I love that if they can keep aggro and properly use cool downs. It's the tanks that pull one mob at a time that really rustles my jimmies.
8. Holy paladins need a healing cool down. Where's my "Oh S#!t" raid healing button?
9. Did I mention standing in stuff?