GTA: SAS Zombie Assault TD
No one knows where they come from and when it started. We just know one thing and that is not to let them in the city. The city would be surely devastated if they would get there. Sure, this is a dangerous job, but the military has trained for a lot of things in their training camp. They are our last hope and we need to rely on them. The game is a tower defense and you need to erect different towers to stop the zombie hordes. You can upgrade the towers once you have enough money. Each kill earns you money.