I'd like to start off by saying that before I even knew about the term "film noir", films like It's A Wonderful Life and the Maltese Falcon were staples in my movie library. In fact, I am always one to argue that, while I do enjoy watching It's A Wonderful Life during Christmas season, the film is so much more than a Christmas film. I feel like that is so lost in this day of age where the film is on constant repeat, but only during the Christmas season.
In fact, I'd be more willing to argue that the film is simply a "Film Noir" that takes place during the Christmas season. For example,