Akuji: The Heartless (PSX)

Invincibility:
Pause the game, hold L2 or R2 and press Right, Right, Left, Triangle, X, Up, Circle, Left.
Infinite Spirit Spells:
Pause the game, hold L2 or R2 and press Left, Triangle, Left, Left, Circle, Left, Triangle, Right, Circle, Up, Up, Down.

Debug mode:
Pause the game, hold L2 or R2 and press Left, Up, Up, Triangle, Right, Square, Left, Triangle, Up, Down, Right, Right.