Silent Running

Silent Running is a Fallout, Fallout 2, Fallout 3 and Fallout Tactics Perk.

Fallout, Fallout 2 and Fallout Tactics
With this Perk, you now have the ability to move quickly and still remain quiet. You can Sneak, and run at the same time. Without this Perk, you would automatically stop Sneaking if you ran.

Fallout 3
With the Silent Running perk, you gain an additional 10 points to Sneak, and running no longer factors into a successful sneak attempt. Drastically increases your ability to crouch-run through buildings getting free sneak criticals on everything in sight. This perk also eliminates the added noise generated from having heavier items equipped, so you no longer receive a penalty for sneaking in power armor with a Fat Man in your hands, for example.