Good Multiplayer FPS?

Got to go with Battlefield: Bad Company 2. Tons of unlocks and the most epic battles I've ever had online.

It sounds like you want a game with unlocks. If you want a game just for unlocks, I find if kind of ironic that you want free 2 play, not pay 2 win. Regardless of it's it pay 2 win or just a standard unlock system, you're looking to get an unfair advantage over time vs somebody who hasn't been playing as long as you or somebody who isn't willing to spend some extra money.

That being said, my favorite online games on Steam are: Team Fortress Classic, Day of Defeat: Source, Battlefield: Bad Company 2, Shootmania Storm, Tribes Ascend, and Killing Floor.

Play a game because it's fun, not because there's a self sense of achievement by unlocking weapons because of how much time you have. I'm all for a level playing field from day 1 that anybody buys a game, whether it's release day or the year after.

any of the Counter strike series. You just can't go wrong

If you want something free, try Blacklight Retribution