It's an awesome third/first person (FREE) online multiplayer shooter, but not a lot of people have heard about it. Any PC gamers should definitely try it, if you do send me a friend request my username is screamstoawaken. You can download it here http://www.thewarinc.com/game/ It is free, so try it and see if you like it!
I like World of tanks but Age of Mythology used to have such a good online experience even though it wasn't exclusively multiplayer. But then several years passed and people stopped playing it.