Killing floor

This is another popular zombie game for the pc, well the zombies in this game are actually called mutants, but its the same basic concept as zombies. This is slightly different from left 4 dead because there is no destination point. The point is just to survive. The mutants come in waves, more and more come as the waves pass. You can play alone or online. As you play, you level up different skills depending on the weapon you use and as you level, you can begin playing on harder difficulties. When you reach the final wave, you have to face the boss. This is a huge mutant with a machine gun as an arm and many other scary qualities. He is also a huge powerhouse, can deal a lot of damage, turn himself invisible, and can slowly heal himself over time which can be a pain to defeat. This can provide a lot of entertainment when played with friends.