Faithful Protector

Faithful Protector is a companion perk in Fallout: New Vegas. It becomes available to Rex if Rey's brain is used in the quest Nothin' But a Hound Dog.

Effects
Faithful Protector increases Rex's attack damage by 25.

Quick walkthrough
There are three options for retrieving the brain needed to unlock this perk:
 * Just walk in and kill Rey. This option turns Old Lady Gibson and her other dogs hostile if the player character is not hidden while doing so.
 * Talking to Old Lady Gibson will reveal an option to give her money, in which she will take Rey off to the side and kill him in private; giving you the brain afterwards.
 * Alternatively, you may pass a Barter check, in which case she will do this for free.