My favorite movie right now is The Third Man. My reasons? It's a combination of the locale (Post-War Vienna), the actors (Joseph Cotton, Orson Welles, Alida Valli), the story, cinematography, and music. Graham Greene's screenplay is slippery, featuring characters with multiple dimensions. Holly Martins (Joseph Cotton) comes to Vienna to visit his old pal Harry Lime (Welles). When Holly arrives, he soon finds out his friend is dead. That's just the tip of an iceberg that contains blackmail, black market drugs, murder etc. It's great storytelling.
Orson Welles, though he only appears toward the latter third of the film, is just right in this movie. I can't imagine anyone else playing this role as well as he did. Orson Welles tends to dominate any scene he's in. Watch and you'll notice the way he uses his voice to act. I don't think he would ever be considered a great physical actor. I think he expresses a limited range of physical and facial motion. What he lacks in those departments, he makes up for in voice. There is nothing like hearing Orson Welles talk. I would have loved to share a lunch with him and chat and listen to him.
Few films have as iconic a soundtrack as this one. It's the zither music here by Anton Karas that hypnotises you and brings just the right intrigue to this film that gets better with each viewing. Check out "The Third Man Theme" below by Karas.