I'm just an average zombie player, but more than anything I hate this one scenario that keeps me so frustrated :
10 yr olds that constantly go down in the early rounds, and curse the **** out of you when you don't try to revive them while a horde is following you. Just complete ignorance. I am GONNA REVIVE YOU! Just give me a freaking second. Then they call you a dick and quit.
My solution: if someone quits there should be a 10 sec invincibility or a limited power weapon drop or meat. Something to help you get to the next round and strategize how to continue with a man down.
... And also, the ee isn't over yet