Giant Rat (Fallout: Brotherhood of Steel)

Background
These range from your typical starving, disease-ridden wharf rats to a somewhat larger - and hungrier - mutant, Chihuahua-sized rat. For some reason they appear to have survived the atomic bombs of the Great War and continue to multiply. Even after the Great War, the people see them as vermin. Later, they are considered as easy prey, so people started to eat their meat. All rats run in packs, but they're not usually very dangerous.