From Matt Stone and Trey Parker (of South Park fame), "Cannibal: The Musical" combines the sense of humor of South Park, some elements of Homer's Odyssey, and the story of Alferd Packer, the first American imprisoned for cannibalism.
Despite the dark source material, I throughly enjoyed the light take on it. The pacing of the movie is excellent, with no parts serving as filler, and the movie is helped by a crew who obviously enjoyed making the movie. The director's commentary makes the movie worth a second viewing, being as entertaining as the film itself. The special effects are a bit crude, due to the movie having been filmed with a budget well under $100, 000, but for the most part it helps the scenes, rather than detracting.
"Cannibal" is a must-see, both because of its status as a cult classic, and because it's absolutely unique among comedies, being the only "cannibal-themed musical comedy" out there.