Iguana

Iguana is a species of lizard, one of the creatures fortunate enough to survive the Great War. Unfortunately for them, they are commonly hunted and eaten by people, most often as the Iguana-on-a-stick meal, very much popularized by a man known as Iguana Bob (even if his meals are not always made of iguanas).

Appearances in games
Iguanas appear in Fallout, Fallout 2, Fallout 3, and Fallout Tactics, but they're always on a stick. A living iguana is yet to appear. However, many enemies state "I'm gonna feed you to my pet iguana," implying not all iguanas are kept as food.

It is worth noting that their appearance in Fallout 3 is suspect, as Iguanas are not native to the northeastern United States, and most likely could not have existed in the wild at the time of the Great War. It is possible that they came from pet stores.