Press L1, R1, L2, R2, Square, Circle, and Triangle at the main menu. Starting a new game will give you the Soul Reaver and Iron Armor.
Bonus FMV Sequence
Press Up(2), Down, Right, and Left at the main menu.
While at the title screen of the game enter: Left, Triangle, Right, Triangle, Down, Circle, and X. You'll have bonus DVD material.
Press start during the game hold R1 and enter Down, Circle, Triangle, Up, Right, Circle. Your Reaver should be fire now.