Planetside 2. A great free-to-play shooter and I highly recommend it for anyone who's a fan of battlefield-style games. However, PS2 is like a sci-fi Battlefield on lots of roids.
Some of the battles, just my god. You won't be the same after playing.
Also Insurgency, which is nearly everything I've ever wanted in a shooter. Most notably, bullets that are, like, well, bullets! An insane amount of awesome for anyone craving more realism in their shooters and a steal at $13 on Steam.