Abomination

Abominations are the result of alien experiments on abducted humans. They are found only aboard Mothership Zeta, in the Biological research laboratory, above the Capital Wasteland in 2277.

Biology
From what can be ascertained through various Alien Captive Recorded Logs, abominations are captured human male or female test subjects hybridized with alien DNA, intended to be used by the aliens as biological weapons. The transformation process (of which the details are unknown) turns the subjects into feral, menacing creatures - hostile to anything that is not one of them (including the aliens that created them), and they lose all discernible sexual characteristics, leaving them with an androgynous appearance. It is unknown if there are more of them on the ship after finishing the Mothership Zeta add-on. Their known creation history and asexual appearance seems very similar to super mutants, while their hostile behavior and lack of self-preservation mirrors that of the feral ghouls of the Capital Wasteland.

Gameplay attributes
When spotting a target, an abomination will point and wail loudly (possibly to rally others of its kind), then move quickly into melee range to attack with its long arms. Their attack methods are very feral ghoul-like. They are a fairly standard opponent and are easily killed with alien weapons. When killed, their bodies often contain various conventional alien items such as the alien power modules, or alien epoxy. Sometimes, however, they contain items commonly found on the bodies of feral ghouls (a pack of cigarettes, pre-War money, harmonicas, human flesh, baseball gloves, teddy bears, bobby pins, etc.), which serves to reinforce the abominations' human origin.

Appearances
Abominations can only be found in the Fallout 3 add-on, Mothership Zeta.

Behind the scenes
The way that the abominations point and screech when they notice the player is a reference to the 1978 remake of the movie Invasion of the Body Snatchers, in that, the alien "pod-people" point and screech in the same way whenever they discover a real human.