Zombie Edition is a mod based on original half-life concept, but you will play as a headcrab and, what is more interesting, as a zombie. Zombies can mutate to change their characteristics into three types and every type will have at least six upgrades including new weapons and abilities. For further information please check this mod's Official Page.
List of bugfixes: 1. Door on zlab1 and pile of wood on zlab2 now works properly. Alas, you will need to go to this maps from previous, your saves made on this maps won't work. 2. Level changing from zlab2 to zstr0 now works properly. 3. Mutation menu now will properly show you upgrade info after save/load. 4. Fixed fields of views of NPCs. 5. Fixed sentences, so scientist won't say something like "stop attacking, he's a friend" anymore. 6. Some problems with missing files have been solved. 7. Barneys now fire they guns properly. 8. Human grunts won't have their muzzleflash sprite inside their weapons anymore