On the level where you have to blow up the explosive carts, at the very end where you have to destroy the last cart, instead of shooting the cart with a arrow or throwing an axe, go up to it and use the move where you hold Triangle and destroy the last cart, and the scene will go on and it will show you with either your sword or axe on fire (for Aragorn and Gimli) and for Legolas his swords will be blue.