World of Tanks
 

http://www.worldoftanks.com/about.html

From what I can garner, this is basically an team-focused MMO where your character is a tank. Apparently, it's realistic so you won't see Panzer 2 shells penetrating Sherman armor and whatnot. The closed beta is due to start on July 8 and I just sent my application. Best of all, it's FREE! It also has good graphics.

Screenshots: http://www.worldoftanks.com/screenshots.html

If you want a beta key, go HERE. Hurry, there's only 3,000 beta keys. After that go register HERE, download the client and wait until July 8 to play.