Quality multiplayer FPS

I feel like playing some FPS online and I have no idea what to get. The main FPS titles I know are, sadly, BF and CoD, either of which I'm reluctant to get, since there's a new game released every year, which I'm not a big fan of. Could you guys maybe introduce me to some other FPSs with multiplayer? F2P would be cool but doesn't have to be. Can be military, futuristic or whatever, doesn't matter.

COD has released every year, BF3 is now 2 years old (such a difference I know!), Killing Floor is always a classic MP game. Very cheap and on sale on almost every Steam sale. Planetside 2 is amazingly fun as well, and its free.

are you one of these tactical softcore fps types or would u like to try a real twitch shooter on for size?

if your the former TF2 is an amazing game and CSGO i here isnt bad

if the latter quakelive and tribes: ascend

TF2 is free. CS (either GO or source) are cheap but competitive. Tribes Ascend is free to play futuristic. L4D and L4D2 are cheap fps with zombies with co-op.

There's also Planetside 2.