Unturned

Unturned is a sandbox game in the multiplayer survival genre. Survive the zombie infestation with your friends! Over the course of a typical adventure you'll fortify a base, scavenge for supplies, live off the land and negotiate with other players. The game is being developed hand-in-hand with the community, and tons of features are based entirely on feedback:

Fortification: You can build massive forts out of structural building blocks, or barricade smaller buildings from before the apocalypse began. It is also possible to create traps and intricate electronic systems. These extend to vehicles as well, you can make a giant rolling fortress!

Survival: It is entirely possible to live off the wilderness by harvesting resources, fishing, growing crops and hunting down animals.

Explore: There are several openworld locations to visit from Prince Edward Island to Russia, with many more available in the Steam Workshop.

Bandits: In PvP servers you can battle other players to steal their gear, or play Arena mode servers for a last man standing experience.

Heroes: In PvE you can team up with other players without fear of death, or create a group and work together in PvP! You can also progress Unturned's story by helping rebuild society questing with NPCs.