Bonus Movie:
At the main menu press: Up, Up, Down, Right, Left.
Extra Items:
When approaching a checkpoint do not mark it, jump over it and search the area for any Vampire Relics or any Lore you can get from fights. Then go back and activate the checkpoint. Save the game then reload. All the relics will be restored and all the peasants/guards will be alive again.
NOTE: Once your Health Vial is the equal to your Lore Vial do not exceed the amount in your Lore bar because your Health will reset to what it was at the start of the game, making it impossible to finish the game.
Unlock Soul Reaver and Iron Armor:
At the main menu press: L1, R1, L2, R2, square, circle, triangle. Now start a new game and Kain will have the Iron Armor from Blood Omen and the Soul Reaver weapon as well.
Note: You cannot pick up any other weapons, and the Soul Reaver is indestructable.