Cyberdog

Cyberdog is a generic term for any dog that has been modified robotically. For some dogs, such as Robodog of NCR's Dr. Henry, the modifications are basically physical modifications, such as robotic enhancements to limbs. Others, such as K-9 of Navarro's Dr. Schreber, are more extensively modified, with enhancements to the brain and vocal organs allowing intelligence and speech.

Fallout: New Vegas
In the quest Nothin' But a Hound Dog, there is a cyberdog who is a possible companion in Fallout: New Vegas called Rex. Dr. Henry, a character from the original Fallout who worked on cyberdogs, is the character who performs the brain surgery on Rex. Rex is a fairly decent companion granting a perk which allows the PC to see items while zoomed in. The items will be highlighted green.

Although Rex has a low DT and can be downed quickly, he can be upgraded by replacing his brain with three other dog's brains found in the wasteland. Dr. Henry, a character from the original Fallout who worked on cyberdogs, is the character who performs the brain surgery on Rex. The following is the effects the different brains will have on Rex:

Lupa's Brain from the Fort, which brain increases Rex's health from 450 to 550, Rey's brain, which increases Rex's Attack, an NCR Guard dog brain, which has no effect, and the brain from Violet's guard dog Violetta that can be acquired during the quest Three-Card Bounty, which increases Rex's speed.

Achieved
In Fallout 2, one may be obtained at the New California Republic if you inject a super mutant of your choosing with a sort of chemical that supposedly stops genetic damage. This quest is received from a scientist, and after you report your results back to him he will reward you with Robodog.

Appearances
Cyberdogs appear in Fallout 2 and Fallout: New Vegas.