This isn't really a "classic," but it's one of the best movies out there, and I can certainly watch it again and again; Back to the Future. In terms of true "classic," I'd have to go with Creature from the Black Lagoon. Not all that popular when first released, not really popular now, hasn't even gained a cult following, but I believe it's a hidden gem. Check it out if you haven't seen it!
all beatles movies gone w/ the wind west side story the sound of music charlie chaplin movies laural and hardy movies the 3 stooges movies