Combat Arms http://combatarms.nexon.net
This is a pretty good multi-player, modern day shooter. The game really is free to play, and there is a good selection of character and weapon upgrades using the in-game credit system. The graphics are nice (not quite Crysis) and the game play what you would expect for an online shooter; team death match, every man for himself, capture the flag, etc. The player leveling system is decent and I was able to go from Trainee, Recuit, to Private in a few hours of play.
I have spent a good portion of the weekend playing this game, so I can say from experience it is a great value for the money (FREE). There are additional upgrades you can buy with real money, but don't feel like you have to. As an experienced FPS'er I had no problems ranking high in matches with the "free" equipment. No credit card information is required to play the game. Just go to their website, create an account, and download the game.
