La sortie des usines Lumière

The 'plot' is outlined by the title: the film consists of a single shot of workers leaving the Lumiere factory, and the film would be of virtually no interest (except to students of late 19th century clothing) were it not for the fact that it was the first film ever to be projected to a paying audience, and is consequently one of the most important films in the history of the cinema (IMDB).