I am really enjoying Heroes and Generals its a ton of fun give it a shot I have not spent $1 on it and am very competitive usually top 4 rank in battles.
No game is actually free. They need money from somewhere
Neo Tokyo
Team Fortress 2
Blacklight Retribution(people claim it's pay to win but I've never spent a penny on it and I constantly find myself in the top 4 best k/d in every single match)
There is a free version of Arma 2, used to be on steam only difference between it and the pay version was better graphics on the one you pay for.
Planetside 2 I don't personally like but I also don't see it as pay to win since I never find myself in any difficultly, the game just isn't my style of game.
Tribes: Ascend
War Thunder.
Not sure if you could say its not play to win but great game nether the less.
It's up to you if you want to spend money or not so yes its free if you want it to be.
Unturned
I can atest to War Thunder being a good F2P, it's aircraft based to it's not really a FPS unless you use the cockpit view.
Quake Live
I don't think the OP wanted recommendations. I think he was making a recommendation.
Update : I have been grinding this game for a month and having a blast I am on the german faction look for [TeKSyN]Kevin if you are playing. Also there are a couple of Teamspeak servers dedicated to Heroes and Generals now as well. I highly recommend giving it a try its the best WW2 game I have ever played and the best F2P game as well. It does take a long time to grind but I like that aspect of it. There is no pay to win aspect in this game at all it takes dedication to dominate.
You are correct sir I was recommending a game not looking for games to play.
Defiantly check out Planet Side 2 and Tom Clancy Ghost Recon Phantoms .. both free to play .. one is huge open world (thousands of players at a time) the other is small team based/oriented game play ... both are really fun.
Fistful of Frags is fun. It is basically CS Source but Old West. It takes some skill because accuracy is really important due to loader reload times and much smaller clip size.
Star Trek Online, and yes, SWTOR.
Team Fortress 2 is what I would recommend. Incredibly fun and in no way is it pay to win. Tribes Ascend used to be cool but it is pretty pay to win now and it is glitchy and buggy as hell. Plus it doesn't have a huge community.
+1 TF2
World of tanks
Loadout is huge fun as well.