Snake

Snakes are legless, elongated reptiles classified as part of the suborder Serpentes before the Great War. Afterwards, a number of species have mutated into forms resembling snakes. Although they have yet to appear directly in a Fallout game, the suborder has survived and even thrived, judging by the amount of snake-related expressions and several names that appear throughout the games.

Variants
All of the following variants were planned for inclusion in one or more games, but were cut.

Pit viper
The pit vipers were giant snakes worshiped by the Vipers. Killian Darkwater mentions that fact as well, though he does not identify them by name.

Hag snake
A hagfish that mutated into a form resembling a snake.

Two-headed rattlesnake
A monstrous snake with a bifurcated spine and two heads, bred by the Vipers out east.

Texas Rattler
A giant, mutated rattlesnake. The mutation has diluted its poison, making it merely sickening instead of lethal, but it has also made the snake into a giant, monstrous reptile. Coming in at six feet tall (over 180 cm) and with 500 pounds (225 kg) of weight, it doesn't need the bite to kill a full grown man.