I'd go for Red Orchestra..one of the best games i've played in a long time. Steepish learning curve, but once you've played for a while other games like COD or DOD just look so simplistic and boring.
Features:
No Crosshair. Your gun when shooting from the hip doesn't always shoot in the centre of the screen - you have to judge the angle of the gun to shoot accurately from the hip and the angle changes as you move the mouse around, up to a maximum angle at the sides of the screen. If you have the time though you should go to iron sights (you get iron sights for every gun).
Limited classes. So basically not everyones running around with the SMG's..depends on the map but often you will be using a Bolt Action rifle. I often take the bolt when theres a choice of SMG, semi-auto or bolt, so don't feel like your stuck with a crappy gun. Reason being that although you have a slow rate of fire, at least when you shoot you know your shots going to land where you point. Theres a lot more deviation with the semi's and smg's and theres some hefty recoil. Depends on the map..if its mostly close range then you're better off with the smg or semi-auto, although you can do well close range with a bolt if you get good at hip shooting. And of course you get a bayonet with the bolt
Balistics. Each shot fired has its own velocity, which depends on the gun its shot from, so it takes a little time for it to travel to the target. This means you have to shoot slightly infront of the guy you're shooting at (which depends on their distance away from you and how fast they're moving). They also dip a little as they travel, so you have to aim slightly differently depending on how far away they are. With a bolt bullet dip isn't really noticable. SMG's fire a slower round so its a bit more obvious with them. But they aren't accurate enough to use them at those types of ranges anyway.
Sounds - great atmospheric sounds, each with a seperate sound depending on how far away the shot was fired. Inbuilt voip for commanding your team around
Maps - theres full tank v tank combat maps, combined arms or just infantry v infantry. I prefer infantry v infantry, but if you like tanks theres a full ballistic system for them too. Each tank has weak points where they blow up in 1 shot as long as you penetrate. Penetration depends on armour thickness, cannon, and the angle of the tank (angling increases armour thickness). You can get data charts off the RO website showing ammo boxes and engine locations. Shooting the ammo box blows em up in 1 shot, engine shots disable the tank, and you can shoot the tracks to disable em too...though its a bit buggy shooting the tracks atm. The view distance has recently been upgraded to about 1400m, but for most maps its about 800m I think. Theres a v good variety of maps too, short, medium and long range ones, about 13 stock maps, and many custom maps too.
Gameplay is some of the best i've played in years..I can't get enough of it

. It requires skill and a bit of tactics to play well - having good aim, using cover, attacking as a team. You basically have to capture objectives by moving into them with your team mates..the more team mates you have than the enemy in the capture zone the faster you cap it. It really helps to play with good players, so try to join a server with clan members playing for the best experience. I tend to play on the Splat server..they play most days and theres a good bunch of regulars who play there too. Thats one of good point about the game.,.the community is generally a lot more mature than you find in other games like DOD or COD, and i'm yet to see a cheater since I started playing last March.
And another thing - this game gets some of the best support from the devs I've ever seen..regular patches and they keep a close eye on the forums and listen to suggestions.