Marked

Marked is a perk in the Fallout: New Vegas add-on, Lonesome Road.

Obtaining the perk
In order to obtain the perk, you must kill any three of the following named marked men: Blister, Bonesaw, Blade, and Beast. You should be able to obtain this easily during the Lonesome Road main quest, unless you are attempting to use stealth to get through it.

Effects
This perk gives you a bonus of +10% Damage Resistance* and +10% damage against marked men.

Bugs

 * It actually gives you +10% Damage Threshold, not Damage Resistance.