Just going to throw World of Tanks into the MMO ring of doom and destruction.http://worldoftanks.euhttp://worldoftanks.com
A free to play MMO in WW2 era tanks. Blasting the crap out of other people in tanks. Each battle is a PVP team based affair on maps 1km^2. Shell penetration and armour thickness is realistically modelled (though aspects of the game are tweaked for more fun and accessibility).
It's taken a free to play, with optional micro payments, approach. So you can spend no money at all and be at no disadvantage. Or you can pay, and you gain money and xp faster than normal, meaning you get the bigger tanks sooner.
There is company /clan / guild mode coming soon, where your clan leader picks an area on a map of Europe (possibly north america for those playing on the US server) and if it's occupied you have clan battle against the current occupiers, the winner tanks the area and any resource bonuses that come with it.
I'm liking it a lot, though I don't really have time to play much of anything any more, hopefully the windows VM I'm installing at work can run it on night shifts
It's been out in Russia for over a year, and had a worldwide release 2 months ago, so it has masses of polish already.