It's a toss up between this one and Peter/Edmund brotherly relationship or Susan/Lucy sisterly relationship or Peter/Lucy sibling relationship. Sorry Susan/Edmund sibling relationship, it didn't do it for me.
This scene in "The Voyage of the Dawn Treader" is my absolute favorite in any of the Narnia books OR movies. It's incredibly powerful, moving, and emotional all at once. I cry like a baby every time I see or read it.