Gimme Shelter (the Stones documentary)
Ever seen
Cocksucker Blues? That's the movie the Masles Bros. originally released, but after the Stones' management decided it wasn't a good idea to show footage of the band members shooting up, cavorting with naked groupies, and generally being the Stones, so they took the film out of release. You can find bootleg copies every so often.
Gimme Shelter was the compromise, using only footage of the Altamont show, rather than a tour documentary.