Christopher Lee is great... there's an utterly non-book scene which I love immensely, the one where he commands the storm on Caradhras from the top of Orthanc. By the way, he's of Italian origins (his mother is a Carandini) and you can hear it in his enunciation in that scene!

I forgot another one that impressed me a lot, that is Karl Urban as Eomer. I thought he was too much of a "pretty boy" until I saw him in character. He fills that armour well, and I don't mean only in a physical way. *G* The "Oaths you have taken" scene and the one when at Pelennor he charges laughing and screaming balancing the spear in his hand are very powerful, I think. I'm looking forward to seeing more of him in the EE, especially when he finds the dead Theoden and the wounded Eowyn on the field.