War Thunder WWII sim
 

This is without a doubt one of the most enjoyable and addicting games I've played in a while.
It's a WW2 themed MMO except its not persistent as WoW is.
It's more like Battlefield 3 or the like.
Oh, it's gorgeous to play and free!
One suggestion though is to change the controls to Mouse or you'll never get past the tutorial.
I've got a buddy I fly with on Skype so PM me if you ever get the urge to play and we can squad up.