The Fountain is one where if you were watching the movie you'll truly have a better understanding of it. Still Epic in so many ways and is really compelling.
In Sunshine, Capa's was really thought provoking. The few seconds where its "still" gets me every time. Great ending with whats shown afterwards as well.
I think Captain Kaneda's is the one I can watch over and over again. Its one even if you didnt see the movie.....You can watch on youtube and still understand the emotions. A man so hypnotized by the Sun that he'll rather die trying to see something beautiful. Its a horrible death...but at least he saw something no one has ever seen. It was truly epic.