Extreme Speed (3.5e Feat)
From D&D Wiki
Extreme Speed [Fighter, Assassin]
You have trained your body to the point of being able to move at supersonic speeds.
Prerequisite: Dex 20, BAB 5
Benefit: Double your base movement speed for all forms of travel (walking, swimming, flying etc.) This stacks with the run feat while running. This feat affects each form of travel only once (eg. fly speed is based off of land speed most of the time, the feat only affect the base of the flying speed directly the base land speed for it is still calculated off of your normal base land speed.
Normal: Normal movement speed