Duck Soup (DVD)(1933)

This political satire starring Groucho, Harpo, Chico and Zeppo Marx is often considered the Brothers' funniest and most popular film. After being appointed dictator of Fredonia, Rufus T. Firefly (Groucho) proceeds to bring the mythical nation to a halt by showing up late and insulting everyone at his inauguration. Hoping to oust the unfit new leader, two spies (Harpo and Chico) are sent from the neighboring Sylvania. Soon enough, war is declared between the two nations with outrageous results. So funny it earned spot on AFI's 100 Years... 100 Laughs list.