not a *steam* game but it is enjoyable titanfall(can be found low as 10$ now), but since cod aw rip off the ideas there are less people in servers of titanfall now, or if you want steam fps game trust me payday 2 is the one of best coop fps i have ever played.. due to playing too many competitive fps games(cod,bf,titanfall) i really enjoyed the gameplay it have offered with role playing games like skill tree system