68 characters IGDB has catalogued for Fallout 3.
Mom
Mr. Brotch
Mr. Burke
Narrator
Nathan
Old Lady Palmer
One Year Baby
Overseer
Paladin Gunny
Paladin Vargas
Pinkerton
President Eden
Reilly
Scribe Rothchild
Sentinel Lyons
Sergeant RL-3
Sierra Petrovita
Stanley
Star Paladin Cross
The Great One
Three Dog
Timmy Neusbaum
Tree Father Birch
Tulip
Young Amata
Young Butch
Young Paul Hannon
Young Wally Mack