I could list a ton but I'll go with my personal pet peeve first.

Healers

Ok, Tank hasn't lost any HP yet, it's ok I'll stand here and wait while they fight. Hmm, still no damage. Should I throw out an Aero or Stone? Nah, I'll keep watching. Ok! 4 damage! Cure II! Cure II! Cure II! Ok, now back to waiting...