make the game about like movie resident evil - you could have them wake up in an underground bunker in a hospital like room and they have to find they're way out of the bunker and escape by mine cart up top to a big manison - but the fun and danger only increases as now they have to escape the city to get to a safe zone - the players start out in the game with nothing and will have to find food and weapons on the way to survive - this could be set up as a reward if they can escape - not only will they have to watch out for the Zombies but other players also for this will be a full pvp survival zone.