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:
 * Murdering 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 pay for the brain. Old Lady Gibson comments on Rey's long life, and will help Rey pass into the afterlife, giving the brain to the Courier.
 * A Barter check of 70 can be used to avoid paying the caps when speaking with Old Lady Gibson.