Zombie riot is a mod that allows you to change your counter strike source dedicated server into a co-op zombie hunting, like Killing Floor. You can configure the zombie waves, the number they come in, zombie types and skins, health...
A greater zombie pack
Use "View Original" to view it on a white background in case you can't see clearly on the transparent background, sorry for the image, it's the best I found.
Is their an arm growing out of that guy's stomach o_O?
ghost_rider,
Lol firstly I looked at this too xD