Been enjoying 7 Days to Die lately (alpha on Steam). FPS Zombie/base defense game. I like that the focus is on the zombies rather than PvP with a few zombies thrown in like DayZ. 7DTD the zombies are a real threat and will beat you down with random hordes that can run up to several hundred zeds per player in the area. Every seventh day there is a major horde that has figured out where you live and comes for you. On the seventh of those hordes (there's more each time), I had 600+ zombies just for me. They zerg rush you and different types have different abilities, you have to have a solid layered defense if you want to survive...and you only had 7 days to build/rebuild it (about half an hour of game time per day + 10 minutes of game time per night). Oh, and they have a map mode where there are no boundaries, it's completely random and you can just keep running in one direction forever.
Mining, building, scavenging, exploring and mad zombie killing fun. It's worth the cash IMO.