This mod brings headcrabs to Garry's Mod -- but that's not all. Not only are they props, they spawn! Now they become actual terrifying headcrabs from within the Half-Life universe, thanks to Steam user Shakes.
They can latch on to NPCs or players if those NPCs or players die, turning them effectively into headcrab zombies. This is perfect for a potential Half-Life RP server or possible zombie game mode.