Ochaken no Yume Bouken (Japan)
Oddworld - Munch's Oddysee (Germany)
Oddworld - Munch's Oddysee (USA, Europe)
Ohanaya-san Monogatari GBA - Iyashikei Ohanaya-san Ikusei Game (Japan)
Ojarumaru - Gekkouchou Sanpo de Ojaru (Japan)
Okumanchouja Game - Nottori Daisakusen! (Japan)
One Piece (USA)
One Piece - Dragon Dream (Japan)
One Piece - Going Baseball - Haejeok Yaku (Korea)
One Piece - Going Baseball - Kaizoku Yakyuu (Japan)
One Piece - Ilgop Seomui Debomool (Korea)
Onimusha Tactics (Europe)