Z Day is an Online 3D FPS Zombie Survival game (also known as a "MMOFPS"). Players are thrown into the centre of a post apocalyptic city after a deadly virus outbreak has occurred.
LinkEdit: It does seem to be going towards the more realistic survival than normal zombie-horror shooters:
"Use your survival instincts, build a survivors' base, form a search party to go out on supply runs for food, wood, anti-viruses, weapons, more survivors etc. Gather up, meet friends and work together for survival...Teamwork is a must..."
Finally:
"The game will be in released in four stages, each stage will be a game in itself. Each stage will involve taking the previous stage and adding more to it - working up to the final stage which will be a full MMOFPS."