Iguana-on-a-stick

Iguana-on-a-stick, available as a whole iguana or in the form of iguana bits, is an edible food item in Fallout, Fallout 2, Fallout 3, Fallout: New Vegas and Fallout Tactics to replenish hit points.

Fallout 3
Iguana-on-a-stick is commonly found throughout the Capital Wasteland, in containers or being sold by vendors.
 * Iguanas themselves are never actually seen in the game anywhere. Probably due to them being made into this tasty snack.
 * It is possible that the iguanas survived the blast as did the scorpions that were kept for pets as well, and have been thriving off the new increased temperatures, how exactly they get their food is difficult to explain.

Fallout: New Vegas
In New Vegas, the presence of Iguanas is quite possible, since the desert iguana is one of the many species that inhabits the Mojave desert.