If you want more horde-killing action but are tired of aliens and space, then World War Z is a perfect option. The game was developed by Saber, the same team behind Space Marine 2. As such, it uses the same tech to create massive hordes of deadly flesh-eating zombies that fuels the swarms of xenos seen in Space Marine 2. You can play alone or with friends and the game has received numerous free updates over the years adding new content, guns, and more.