The spawns, the lack of balance in weapons since everybody uses the MP40 or a sniper, the grenade spam, SnD spawnkilling, enemies spawn near you in Headquarters, Sabotage takes too long to finish since you will never plant or defuse the bomb, rifle grenades are always annoying and unbalanced since it just takes one hit and you're dead when you have to shoot him several times, most of the iron sights on weapons just suck, everybody uses glitches, when a glitch is patched a new one is found, too much lag, horrible servers, horrible players, no report button, too many levels. everybody camps in tanks and if you're a gunner you just get raped, getting spawned in the middle of an airstrike, SnD teamkilling to defuse the bomb, annoying errors everywhere.
I can think of some more.