[PS2] [Cheats] Onimusha 3: Demon Siege
 

Panda outfit and Michelle's 3rd outfit:
Have a saved game file from Onimusha Blade Warriors on your memory card

Puzzle Mini Game:
Complete all puzzles in the normal game.

Unlock Ultimate mode:
Finish the Oni shooting mini game.

Unlock Original Onimusha swords:
Finish the game with all 3 items from the Phantom Realms.
After, begin a new game to have all 3 swords from the original Onimusha.

Unlock Bishamon sword:
Finish the game with the "Onimusha" rating
or
get the Bishamon sword in the Phantom Realm in Honnouji

Quick Health:
In the Zoo, Stand behind the panda cutout and equip the white vest on Ako and
watch your health go up quickly.

Source? Here it is.