"The end is here. Life as you knew it has gone to hell after the mother of all zombie outbreaks. Now you and the few scattered survivors must band together to survive and rebuild in a 3rd-person action game set in a dynamic open world. You choose where to make your stand, designing and fortifying your home base, performing daring raids for food and ammunition, and rescuing other playable survivors with unique talents. The open, sandbox world develops in real-time, shaped by your actions, dynamically generating content based on your choices and the ever-increasing zombie threat."
State of Decay is an open world zombie-survival game, currently under development at Undead Labs for release on Xbox LIVE Arcade and PC.
Website:State of decay
Facebook page: State of decay FB page
PAX East 2013: State of Decay Hands-On preview: State of decay review
State of decay gameplay: 20 minute gameplay footage
Now, I know the animations aren't the best and there are a few bugs but remember its still in development AND its an XBLA title, not a AAA title. For a game of this size that's on Xbox live arcade, its impressive to say the least, and to top it off, one of the developers said at PAX that's its weeks not months until this game is released.
EDIT: Just to clear up some confusion, this game has been in development since 2009, way before dayz ever existed. So please, before you comment saying "dayz clone", do some research about this game and you'll realise its more than just loot and survive.