I've had an idea in my mind for a FPS zombie game. In my mind, a sort of mixture of Black Hawk Down and 28 Days Later but with more added in. Basically a large city is hit with a virus outbreak, highly mutated rabies with something extra thrown in, and the outbreak basically explodes and infects most of the city. A few hundred or thousand uninfected people are evacuated and the city, basically a large city with a 1,000,000+ population sits on an island so it was cut off by the National Guard. One month goes by and the city is silent, abandoned but not forgotten.
A month later a call comes from inside the city. A small group of survivors has managed to hold up in an apartment building and survive. Their running out of supplies but can still hold on a few more nights. This call becomes a light in the dark, there might still be a chance to retake the city if a small group of survivors could hold out. A mission is drawn up to rescue them and recon the situation on the ground. Two fireteams are selected and inserted into the city via helicopters, one team with orders to rescue the civilians and the other to secure a base of operations at a selected location. Storms have been blowing over the city for weeks and the team is being dropped in a four to five hour window where helicopter flights are possible, that comes into effect later.
The fireteam ordered to rescue the civilians begins to move towards the apartment building and is attacked numerous times by large groups of infected. Now, while this wouldn't be directly told to the player, they don't actually have to fight the infected, but there will be times they won't really have a choise. The problem is they only have so much ammunition, maybe 150-180 rounds for an M4 and 60-75 for a 9mm pistol so they have to conserve ammunition. The city would be a large environment where the player could go in and out of buildings and explore as the exact location of the apartment building wouldn't really be known.
Eventually the fireteam reaches the apartment building and meets the civilians. While the civilians get ready to move the team leader and one of the civilians, most likely a cop, talk about the outbreak in a cutscene. The cutscene would last a few moments before the player is taken back to the outbreak and forced to play as the cop until they reach a certain area. When that's done they return to playing as the team leader and begin to escort the civilians to the rendevous point.
Before they get to far from the apartment building they are attacked, not by the infected but by a former street gang turned cult. Firefight lasts no longer than a minute or two before a large group of infected arrive and cause both groups to break off the fighting and retreat. Fireteam and civilians reach the foreword operating base set up by the other team and the first helicopter arrives to pick up civilians. It is filled but and takes off, but after flying a few blocks is shot down by an RPG from the cult. The fireteam has to go and engage the cult to permit further helicopter flights into and out of the city but by the time they have the weather has gotten worse and all flights are grounded.
The rest of the game is somewhat similar. The player has to again play through the civilian's flashback of the outbreak and then surviving key points through the first few days with missions ranging from search for supplies to defending from the infected and cult. There would be more missions for the fireteam as well, including direct combat with the cult where the player has to be careful of not drawing too much attention from the infected. More civilians can be located in the city, perhaps for bonuses and more playable flashback levels, though all voluntary. More ammunition can be found in gun stores, people's homes and on corpses and more weapons can also be found, though no explosives or automatic weapons, except from cult arsenals.
The final part of the game would be the most difficult. It would begin after a failed mission to capture the cult leader where the cult would launch a major offensive against the foreword operating base, perhaps the former city hall or post office. After holding off that attack the infected would come en mass and soon overwhealm the player. As the Sun rises the team leader decides they stand no chance of surviving in the foreword operating base and the game ends with a Mogadishu Mile style run through the infected and then followed by them while occassionally coming under fire from the cult. Reach the last bridge into and out of the city and National Guard sharpshooters and regular infantry provide you more than enough covering fire to escape, don't reach them and you're zombie food.
