I just got done playing Halo 3 a decent amount for the past week and a half or so. One thing that drove me insane was in a capture the flag game, the opponent would for some reason drop the flag while he was running, and the immediately pick it up, generating a never ending sound of "flag dropped! flag stolen! flag dropped! flag stolen!" and we happened to have a bad team, and couldn't stop them. it was so annoying because it felt like a taunt.
most of the annoying stuff of other people's voices people here are talking about doesn't really annoy me, because im either in a party chat with a friend, or i mute everyone immediately. if it annoys you, it's only your own fault for not muting them.