Project Zomboid

If you guys haven't seen this yet, take a look. http://projectzomboid.com/blog/ It's an indie PC game with realistic zombie survival. You have to eat and drink or you get weaker, food spoils if it's not in a fridge, you can start a fire that actually spreads like it should, it's pretty fun. They've got a demo you can play that has a little bit of story but is mostly just letting you play in the sandbox.