First up is
Blacklight: Retribution out of Perfect World. Pretty much your standard near future FPS. Multiple game modes, ridiculous amounts of customization, and mechs. GODDAMN those mechs rock. Very much a team/squad focused game.
Second,
Tribes:Ascend a unique SUPER fast paced shooter. Its unique characteristic is its "skiing" mechanic, pressing space-bar renders your character friction-less, allowing you to slide along the map at ridiculously fast speeds. It takes quick thinking and a ****ing good shot to do well in this game, stay moving and you'll stay alive.
Again, the best part of this is that they're completely free to play. But if you choose to sink some cash into them, you can speed up your unlocks or get certain unique skins.