http://dirtybomb.nexon.net/

Dirty Bomb takes first person shooters back to their purest roots in a highly challenging team game that will test your reactions and resolve as you battle for survival on the streets of a radiation ravaged London.
Dirty Bomb is a FPS objective based game at the moment (deathmatch may be realeased) This game is currently beta but you can buy the game on steam and get a starter bonus. I played this game for some hours now and I can confirm its not a pay-to-win game, it takes just a few hours to unlock all the classes if you are playing for free.

This game has 7 classes, gonna write my experience with them.

Proxy: which is a fast runner and shotgunner that can double jump much like the scout in TF2, the difference being she have proxy mines. This class is so annoying to deal with as sniper its ridiculous.

Fragger: which is a heavy damage guy with a heavy weapon and frag grenades, this guy is for people that hate team play and want all the frags for themselves

Skyhammer: throw a grenade shape beacon for COD style airstrikes, has a pretty ok rifle as well, good class on open maps where airstrikes are op

Arty: in my opinion the worst class, he is exactly like skyhammer only that his artillery is smaller AOE and you have to aim where you want it rather than just throw a beacon. they both have ammo packs and arty has a worse gun so I see no reason to pick arty over skyhammer

Aura: One of the two medics in this game, Aura can deploy a heal station that heals quite a lot and can instantly revive people with defib with cd between revives, has a pretty good shotgun as well so pretty nice for close combat

Sawbones: can deploy med-packs and defib same as aura, heal is slightly weaker but can be distributed better. Has a pretty strong SMG and more health than aura making him better for solo flying while aura is a better team player.

Vassil: The sniper of this game, the snipers here are pretty weak, the snipers I have tried so far only one shots in the head and takes up to 3 hits in the body which is useless because people will get hit once and run away to heal, so its much like using a scout in counter strike, can also drop a heartbeat sensor which allows him to see enemies through the wall in a small area, but doesn't last very long, his pistol is ok but you still won't stand a chance when you get rushed down.