Dead Alliance by Maximum Games

Dead Alliance is a multiplayer first-person shooter set in a post-apocalyptic world overrun by zombies. Players form teams to strategically seize control of enemy bases on infested maps, using an arsenal from classic firearms to pheromone grenades. They can also turn the undead into allies against opposing factions. Survive against enemy armies and man-eaters while capturing as many bases as possible in this desolate world where your only chance is to use the dead... or join them.