"It's... It's a f- flaw... in the iris."
At his excellent movie blog, girish (aka Girish Shambu) savors those all-important "cinephiliac moments":
...these are small, marginal moments that detonate an unforgettable little frisson in the viewer. The important thing to remember is that these are not moments carefully designed to exert great dramatic effect—not that there’s anything wrong with those—but instead they are fleeting "privileged" moments writ small that we find ourselves strongly attracted to, perhaps even disproportionately so given their scale and possible (lack of) intention.
[Go here to see some of girish's examples, and those of his readers; and while you're there, check out his exquisite and deeply personal (can there be any other kind?) appreciation of Robert Bresson.]
One moment that came immediately to mind for me is from Roman Polanski's "Chinatown," after a quick getaway from the Mar Vista Retirement Home (involving gunfire at a fleeing white convertible Packard) that prefigures the ending of the movie. "Chinatown" is a film about eyes, about partial vision (and doors and windows through which one can never quite see the whole picture). In the passenger side of the car's windshield (the screen-left "eye") has been cracked by a gunshot. Jake Gittes (Jack Nicholson), bearing his own wound on his nose, looks over at the driver, Mrs. Evelyn Mulwray (Faye Dunaway). The top is down, and she delicately brushes hair out of left her eye -- the one that has a "f- flaw... in the iris.... It's a sort of birthmark." This eye imagery will culminate, horribly, in the final moments of the film. It's a small, evanescent moment, and I have no idea if it was intended or if it just happened, but I always get that frisson when I see it.