Poll: Movies with a Minimal Cast

Some movies center on a tight drama involving a very minimal amount of characters (three, two, or even just one). They forego large casts, and that small core pretty much have all the speaking and acting parts. Some of these movies might have larger casts than just that core, but they are either "extras" in one small scene, or voice-only (offscreen). The overwhelming majority of the time and narrative of these films depicts only that minimal core interacting. These films are usually intense character studies, shown in a very small-group (or pair, or singular) dynamic. Which one of these films of that style makes use of it in a way you like best? Discuss here