Like Counter Strike, but without the suck.
Soldat's premise is a simple one. Grab a gun, move, shoot. If you aren't dead yet. Repeat steps twp and three. Seriously though, the game is 2-D, which provides an interesting perspective to a game like this. Using keys, you move left, right, or jump. Simple. Use the mouse to aim your gun, shoot, and hover (a cool feature). Your arsenal consists of 14 weapons based off real-life counterparts. Each one lends itself to a different play style, and you'll soon find a favorite.
Playing online is where it's at in this game. And although initially you will be "teh suck", soon you'll be a force to be reckoned with. Unless you just suck... but even then you can team up with some guys run amok. Either way, simply put, your going to have fun.
The last and best feature of the game is that it is FREE. Totally free to download and play indefinitely. You can register for a few bucks and get some cool options, but you need not pay.
One last thing, this game has a cool little physics engine which causes dudes to crash to the ground, or fall off ledges in funny ways after dieing.
Play this game. It's fun. It's free. 'Nuff said.