Call Of Duty 4, World at War, Modern Warfare

These Call of Duty games use open mic, meaning you just have to turn your mic on and talk. You'll know if the game recognizes your mic in the online lobby because there is an icon next to players that have a mic.  This icon lights up when someone speaks.  In World at War, there is a VOIP option in the Settings menu that lets you change the level of incoming chat from other players and also the level of your outgoing chat.

Killzone 2

KZ2 uses an open mic so just speak! There is also an option to mute individual players.

Battlefield: Bad Company 2

This game also uses an open mic and has an option to mute individual players.

Grand Theft Auto IV

Voice chat is available in all modes. In the game setup the host can choose open mic, and proximity (only people nearby can hear). You can also talk privately with another player by using the in game cell phone. There is an option to mute other players as well.

Guitar Hero III

During the game setup all works well. After a round starts the chat does not function until completed.

SOCOM: Confrontation

This game uses an open mic and has an option to mute individual players.

SOCOM (PS2)
SOCOM games will not work with any Bluetooth headset. You must use a USB mic for older SOCOM games.