Planet of the Apes. The original 1968 movie.
I saw this on TV as a kid, as well as all the sequel movies and I think TV show. I remember finding it so scary and thrilling, and was into what a mind fuck it was -- thought it was very thought-provoking.
But boy oh boy is this cheesy movie. Charlton Heston overacts. The sets and everything look like they were made by high school kids. The whole thing is just very campy. Which I guess isn't a bad thing. I did enjoy myself.