Somtimes I'll mutter, "shit, shit, shit" when I'm under fire and trying to find cover, or when the flag is about half way up and you see the enemy tank rolling in and you're on foot
If someone hops into a vehicle before I can (because they have longer sprint than support) and they drive off without giving a ride I'll mutter "asshole"
If I do something stupid, like not being able to stop in time for the AT Mine/claymore, I give a "damnit"
If I get stuck in the kill/revive loop I'll mutter "stop reviving me cocksucker"
If I think someone is hacking, they get an "aww that's bullshit" when they kill me
...of course I only use VoIP, so none of this is heard by anyone but me.