The first is from The Apartment (1960). A lovely little scene from the greatest of films. Notice Baxter's remarkably direct question to Fran if she's gay. If only it was always handled so casually, like it really was the most natural thing in the world. The film is basically about the immorality of modern life but it's easy to miss since it's such a warm and tender film, so different from much of Wilder's earlier work. It's worth pointing out that Wilder first worked with writer/producer Charles Brackett, from the 1930s to 1950, and that he after that formed a partnership with writer I.A.L. Diamond, from 1957. It's a fair point to say that Wilder's films changed, and became more humane and tender as a result.
The second scene is from Kiss Me, Stupid (1964). It's little known but pure Wilder, and a small delight. It makes vulgarity in to an art form. It's also an example of one thing typical of Wilder, how he plays with an actor's persona. Here Dean Martin's playing a drunk singer named Dino.
The third scene is from The Lost Weekend (1945), a cruel story about a writer who's also an alcoholic. He goes from one humiliation to another during a weekend of angst. It's Wilder's scariest film and the scene I've chosen is one of the writer's hallucinations, and can be interpreted as a struggle between his literary ambitions (the mouse) and his alcoholism (the bat).
Soon I'll continue with more scenes but these three will do for now.