First Person Shooters are among the most played computer video games. They combine navigation, interaction and collaboration in 3D virtual environments using simple input devices, i.e. mouse and keyboard. In this paper, we study the possibilities brought by these games for musical interaction. We present the Couacs, a collaborative multiprocess instrument which relies on interaction techniques used in FPS together with new techniques adding the expressiveness required for musical interaction. In particular, the Faders For All game mode allows musicians to perform pattern- based electronic compositions