Having some fun with this.
http://worldoftanks.com/
15 on 15 shooter like PVP battles, but you're in a WW2-era tank. You start out in something small and fragile, but you can upgrade to better stuff the more XP you earn. (so it's got some MMO elements too). Free to play, but there are micropayments for some additional bennies.
I'm Limekiller on there if anyone wants to look me up.
-Arlos