Project Zomboid - The best zombie game that hasn't been released yet. [now with 50% more release!]

http://projectzomboid.com/blog/ The developers are having trouble with paypal and google so you can't buy the game directly, but if you buy one of their other games you also get a lifetime license for PZ. The other games look like they were coded in 20mins. just so they could have something to show paypal because the online payment services don't like doing "pre-orders". There's no official release date but if you check the forums they only have a couple things left to do before they release the demo.

Edit: The tech demo has been released because some tester uploaded the pre-release. Get it here