Old Yeller, for its daring choice to shy away from sentimentality in its coming-of-age ending. If you haven't seen it, do so. It's one of the few films that make me tear up.
Btw, for those of you who are interested in such trivia, Mary Poppins, Bedknobs and Broomsticks, Song of the South, etc. are not live-action films because they are, at least in part, animated. Some film buffs and scholars call them hybrid films, although that term is fraught with some definitional challenges as well. Still, I like to use it to describe the live-action/animation combination found in Who Framed Roger Rabbit and the films mentioned above. All these films are entertaining, and so I was almost relieved to be able to take them off my list of possible answers due to this technicality.