THX 1138 : George Lucas's first film as a director, just before Star Wars. I wish the guy had a little less dazzling success so we could have seen more of his personnality
THX1138 is pretty special. I'm still trying to find a version without the typical Lucas retroactive CGI spliced in.
Fun fact: there's a scene in the movie (no spoilers) that was filmed, sideways, in the then-unfinished BART transbay tube. If you've seen the movie I bet you'll know which scene.
And while we’re on 70’s TV sci-fi also; The Fantastic Journey, Battlestar Galactica.