The Andromeda Strain
Prescient and brilliant sci fi, from the novel written by a young once-in-a-generation polymath named Michael Crichton, then all of 26 and doing post-graduate studies after Harvard Medical School. Robert Wise' version was notably well-done because the screenplay is for all intents every word of dialogue in the novel to the letter, only a couple of cosmetic character changes, and with precious little screen time wasted on anything superfluous. The effects and visualization of the novel used industry state of the art input, which achieved a film that was not only cutting-edge then, but remains so even now. It was one of the first sci-fi films as such I ever saw, and its appeal hasn't diminished a whit since then.