Centaurs are the result of combining various kinds of animals and people and infecting them with the Forced Evolutionary Virus. These abominations are horribly disfigured creatures with little intelligence and an affinity for their super mutant masters.
Centaurs are, much like their namesake cousins from the west, the result of the Forced Evolutionary Virus being used on a combination of humans and a myriad of animals. The centaurs of the east coast stand almost as tall as an adult human. Their torsos lack arms, and their mouths are filled to the brim with writhing tentacles. Instead of legs, a centaur has multiple human arms which it uses to drag itself along the ground, which confines it to a slow, shuffling mode of travel.
Centaurs are the constant companions of super mutants, used as attack and watch dogs, and as such can easily be an indicator of more serious threats nearby. As individuals, though, centaurs only pose a minor threat to most players. They are decently durable as opponents, and can sustain a rather large amount of damage before succumbing to their wounds, but this is offset by their weak melee attacks in the form of lashing their tongues. They telegraph their close combat attacks quite decisively. Centaurs are also capable of ranged attacks which consists of radioactive spit. The spit does not cause a lot of damage but causes a staggering 5 rads/sec for 15 seconds. They are entirely silent creatures, lacking the ability to produce sounds of any kind, and can sneak up on unwary targets.
The basic centaur variant in Fallout 3. They are slow-moving and often travel with a super mutant. Centaurs have both a long range and a close range attack. Centaurs are not major threats, however they may cause trouble for low-level players.
The following is based on Fallout 3 cut content and has not been confirmed by canon sources.
Clancy was a named centaur cut from the final release of the game. Although identical to normal centaurs stat-wise, Clancy's internal name associates him with the quest Wasteland Survival Guide. Although he cannot be found anywhere in the game, Clancy can be found in the game files. His reference id is 2d3be.
Centaurs are mostly found accompanying super mutants, or may be found in a group, without their masters. Only rarely are they found alone.
Based on concept art, it seems at one point there was to be an "intelligent" centaur.
Centaurs lack the dog head alongside the human one like the centaurs from the first two Fallout games. This may be due to the different experiments with Forced Evolutionary Virus that happened on the east and west coasts.