2. Primer
Primer is without question one of the most challenging and fascinating sci-fi films ever made, and certainly one that benefits from at least two or three watches. It's as close to an authentic movie about time travel as we're going to get, largely because it eschews flashy laser beams and an epic score in favour of a totally grounded, down-to-Earth examination of a man discovering the ability to time travel. This lends the film a curious relatability even as actor-director-writer-and-so-on Shane Carruth rattles off the technical jargon in a manner that suggests he doesn't really want you to get it. What's perhaps most brilliant and sharply-observed about the film is that, if someone ever were to discover time travel, it probably wouldn't be by way of a slick, silver, smoky gadget, but probably a mess of wires and components. This raw quality lends Primer a more authentic feel, as does Carruth's often beguiling dedication to precise technical dialogues.