Centaur

Centaurs are misshapen, mutated creatures. They are a by-product of the Forced Evolutionary Virus, and some of them were created by the Master by tossing a varied mix of humans, dogs and other animals into an FEV vat and seeing what came out the other end. As a result, they can differ quite a lot from one another.

The Centaurs are not only created by the FEV, they also seem to live in a heavily irradiated environment.

West Coast
In the Core Region, centaurs are created by the Master and frequently travel in packs with floaters. They encompassed a large bulk of the Master's armies and are commonly found with the nightkin and other remnants of the Master's army who roam Northern California.

Capital Wasteland
The Centaurs encountered in the Capital Wasteland are physically different from the Centaurs from the Core Region, trading the dog-like head for a human one and the feelers on the back for 3 long, tentacle like tongues. Like their western counterparts, they are created by FEV along with the Super Mutants, so their birthplace is Vault 87. Unlike its core region "cousins", the Capital Wasteland Centaur uses a ranged attack: a high-arcing, slow-moving projectile that can carry lethal doses of radiation. Oddly enough, it is capable of igniting lingering gas vapors as well, indicating some kind of pyrophoric quality. Centaurs are known to accompany Super Mutants as "guard dogs", so if you see one, expect super mutants ahead.

Fallout 3
Centaurs can pose, at best, a moderate threat level to players but are generally a weak enemy. Their weak spot is their long, tentacle-like tongues which can be easily targeted in V.A.T.S.. Usually they don't carry anything, although they sometimes carry chems like Jet, small amounts of caps, and rarely random items like Teddy Bears. They spit slow moving, radioactive balls as a ranged attack which may ignite nearby gas leaks, but is relatively easy to dodge. The damage done by the spit itself is low, but can increase your rads quickly (+4 per second for 10 seconds). When up close, the Centaur whips its tongue at you. This melee attack is rather delayed, usually slower than the player's melee attacks. Centaurs are rarely found wandering alone and so may indicate that Super Mutants are nearby.

Appearances
Centaurs appear in Fallout, Fallout 2 and Fallout 3.