Killer rabbit costume: Complete the game once and unlock the Extra Costume option, then enter the following case-sensitive password. Once entered, you can then choose your costume during gameplay: BlueRobbieWin
Golden rooster costume: Complete the game once and unlock the Extra Costume option, then enter the following case-sensitive password. Once entered, you can then choose your costume during gameplay: cockadooodledoo
God of thunder costume: Complete the game once and unlock the Extra Costume option, then enter the following case-sensitive password. Once entered, you can then choose your costume during gameplay: GangsterGirl

More Silent Hill 3 Cheats
All "button press" cheats are courtesy of CVG