Meatballs is CRIMINALLY underrated. Some of Murray's best work and really the movie that launched his career. There are even some moments when he actually stretches his serious acting chops as well, believe it or not. Anyway, probably no one here will agree with me, but I'll say it anyway: Teen Wolf >> Back to the Future
I will also say "The Way Way Back." I freaking loved this movie. One of the few I own just so I can get others to watch it.