Legacy of Kain: Soul Reaver II
Press Left, Triangle, Right, Triangle, Down, Circle, X at the main menu: A message will confirm correct code entry. If you are taken into a menu, just back out and start again. All of the previously locked bonus materials will now be available.
Get Fire Reaver:
Pause the game, then press and hold R1 and then press Down, Circle, Triangle, Up, Right, Circle.
Thanks to Revolution reader Abel!