Left 4 Dead crossed with Fallout 3...post-apocalyptic Zombie shooter in an MMO world, more interactivity with environment as well such as building/maintaining camps and bases for player guilds to combat others and zombie hordes, with that Fallout 3 black humour from the NPC's and maybe even a little Stalker COP thrown in for that real sense of desperation and difficulty, just with a skill system installed.
That or KOTOR crossed with WoW, oh wait The Old Republic! Gonna blow WoW out of business...hopefully.