This is State of Decay, a new Microsoft-published Xbox Live Arcade game that might be one of the most ambitious digital titles I've ever seen. It's an RPG, and also an RTS, and also a zombie survival game, and also a simulator, and if you're confused by all this, I know exactly how you feel. You can watch some video footage—and listen to me try to talk after destroying my voice at PAX East last weekend—right up top.
Couple of things I would like to add:
Resource management is a vital aspect of the game. You can play as more than one character, people you save join you and many of them become playable.
Did I mention the soundtrack is by Jesper Kyd himself?