It is far from profound to say that films are often intentionally challenging and not only worthy of but inherently designed to require a rewatch (or seven).
The best directors, living and past, want little more than their films to be interpreted, mulled over and exhaustively examined time and again - and what better way to do that than to make repeat viewings the key to understanding the film itself.
Some enjoy furnishing their features with little hints and tricks and subtleties that only become apparent once the viewer knows all there is to know - say, a twist or a high-stakes piece of final act drama; others prefer to layer their films with deeper themes and existential concerns; others still relish convolution and a tight intricacy that needs to be unpicked element by element.
Whatever their tools, filmmakers have succeeded time and again in creating magnificent works of cinema that simply cannot be put down, leading to special editions and commentaries and research papers and entire library stacks of books dissecting their work.
Though by no means a comprehensive list of the films that need a second look, this article nonetheless collects together some of the most fun, intriguing, puzzling or downright ingenious features that cinema has to offer.