Die2Nite is a co-op zombie survial browser game which relies heavily on the players working together in towns (population max of 40).
You are placed in a randomly generated town where you must work alongisde other players to survive as long as possible. You will die, and your entire town will also die eventually. When you die, you get reincarnated and placed in a new town. Any accolades you earn are carried over to your next life. Every morning you're allotted a few AP (Action Points) that can be replenished by eating, drinking, using drugs, or other special events. You have to communicate with the other residents in your town about daily activities and projects via your town's forum.