Hugo Weaving as Elrond in the Lord of the Rings.
I don't know why he just seemed so out of place cast as Elrond. I couldn't get the image of Agent Smith from the Matrix out of my head.
I'd also add Christian Bale doing Batman's voice. I always cringe. He makes a great Bruce Wayne, but I personally find when he is in costume doing the Batman voice it is embarrissing
Christian Bale in general hurts a movie, T salvation might have been salvageable if not for him. I'd love to hire Kevin Conroy to dub all of Bale's Batman lines with his batman voice :lol