PEOPLE ARE FINE IF YOU NEVER SPEAK
Most overused in: BioShock, Half-Life 2, Call Of Duty series, Far Cry 2.
You just try going an hour without speaking to anyone and see what happens. Chances are, it will probably end with being shouted at, or a visit from social services.
Either way people get uneasy around the mute. Especially silent people carrying guns. But in your average FPS, it's possible to make lifelong friends, discover important information and co-ordinate complex attacks on enemy installations - all through the medium of insistent staring.
Order PSM3 here and have it delivered straight to your door