The Third Man (1949)
The Third Man seems to be regarded as film noir by default only, as if it's simply the most convenient way to discuss the film. Of course it's always been a loose genre descriptor, and The Third Man fulfills plenty of the requirements — murder, intrigue, a mysterious woman and sharp, if not particularly hard-boiled dialogue. But the famous score, performed on a zither, tends to work against the cynical nature of the film, lightening the dark corners and shadows particular to the genre, often lending a more lighthearted feel, full of smirk and humor. The darkest, and most interesting element is the setting. Pulp novelist Holly Martins (played by Joseph Cotton) is drawn to post-war Vienna to meet a friend, Harry Lime, who promises work in the crumbled city. Vienna's bombed-out buildings are never too far off screen, lending an added weariness to the otherwise fast-paced mystery.
It has been ranked as the best British film of the 20th century, and it won some Oscars and the Grand Prix at the Cannes in 1949. I liked it a bit less than the hype, but it's good none-the-less. A-