I would love there to be friendly fire, so I can cap someone on the same team camping a doorway or stairs, blocking their own teammates from getting thru. My biggest pet peeve(s) though are: people that don't tell you there's an enemy or betty/claymore by them when you come to defrost; so as a reward for helping that teammate, you die....and if you manage to get an emp off and defrost them anyway, they don't even bother to come back and defrost you, even though they got you killed..... or some people that habitually refuse to move to defrost teammates that are in the same building or otherwise in close proximity. But that'd be opening a whole can of worms...so....