GUN CRAZY is a justly famous 1949 film noir which seems to break all Hollywood conventions of the period, as John Dall falls in lust with sideshow sharpshooter Peggy Cummins, and they embark on a life of crime. Sensual, surprising, and memorable.
Another one I haven't seen, but I've heard a lot about this one. I've wanted to see it for a while, but it never seems to run on Turner Classic Movies. I guess this is the time a NetFlix subscription would come in handy.