Willow

 is a ghoul, the self-proclaimed gatekeeper of the Underworld. She can usually be found on the Mall, wandering around just outside the entrance to the Museum of History.  has a Laser Rifle.

Trivia
The character is possibly a reference to Alyson Hannigan's character "Willow Rosenberg" in the TV series Buffy the Vampire Slayer.

Willow's grammar could use improvement. If you respond, "I'm not a tourist...", she says: "Come on! Here you are in the Mall of our nation's fine capital, taking in the sights, visiting the monuments!" (capital != capitol)

Appearances
 only appears in Fallout 3.