Obscurity factor: 3
This film chronicles the adventures of Donald Duck in the magical land of mathematics. While there he learns about the golden rectangle, pentagrams, circles and spheres and how these and other basic shapes make up the world around us and can be used in games and other pursuits. I first saw this film, as did many others in an elementary school assembly, and enjoyed it immensely - it was a much more fun way of learning mathematics.
I'm not sure if obscure is the word for it, as much as unseen. It's available on DVD and many people know and remember the film, but it's rarely seen today (unless they're still showing it in schools!). Above is part one of 3, uploaded to YouTube by pookzta.
Obscurity factor: 3 (well known, but rarely, if ever screened today, available on DVD)