This literally changes ever week for me, but right now, I'll go with John Carpenter's Halloween. I watched it for the first time in a few years this past week, and I really saw something special in it. It's got everything; a solid script by Carpenter and Debra Hill, a lot of solid performances highlighted by those of Curtis and Pleasance, great direction, and absolutely brilliant cinematography, and it manages to avoid all of the traps and pitfalls that plagued the rip-offs and imitations and sequels that followed.