Otari
Othello
Other
Other Guy
Otis
Otter
Otto
Otto Octavius
Oui
Ouija
Ouisa (oh-wee-sah)
Our Gigi
Outi
Outlaw
Outrigger
Ouzo
Ovale
Oven Mitt
Overboard
Overdrive
Ovid
Ow!
Owas-sa
Owen
Owl
Ox
Oxford
Oxley
Oy
Oyen
Oz
Ozma (after the character in "The Wizard of Oz)
Ozone
Ozu
Ozymandius
Ozzie
Ozzy
Ozzy Pawsburn