I came across Combat Arms a little while ago and thought I would share it here. It is a free online FPS, but you will have to get a free Nexon account.

Prepare to drop into an ever-changing theater of conflict, where you are in control of your gameplay- from your fully customizable character, to your lethal arsenal of weapons to the scenarios you want to experience. Experience fierce battles online with up to 15 of your friends (and enemies) in dense jungles,frozen tundras, industrial wastelands, and more!

Grab your gear and get ready for battle…

One of the more interesting features is that you get “gear points” the more you play that you can use to “rent” better gear.

Character Customization
If you forget to bring it with you onto the battlefield, you’ve only got yourself to blame! Over 30 real word guns, from assault rifles, SMGs, to shotguns, are all at your soldier’s disposal, along with secondary weapons such as different grenades, LAW rockets, and mines. In addition to weapons, your soldier can be tricked out with various camouflages, helmets, vests, and cosmetic items such as berets, bandanas and sunglasses. Every month new items will be added that can give you a new tactical advantage on the battlefield – so keep your eyes out for them!

Modifiable Weapons
All weapons can be additionally outfitted with attachments such as silencers, scopes, and extended magazines. Custom tailor your gun according to the needs of your mission!

Enjoy