Salò, or the 120 Days of Sodom

Surely there are better ways to convey a powerful message about fascism than having to sit people through 2 and a half hours of mind numbingly bad scat play and horribly forced sadomasochism.

Leaving that aside, if you've ever wanted to experience a mix of pure, unmitigated boredom equivalent to that of watching an old folks home production of Arcadia while having the wrenching desire to vomit uncontrollably and cry blood, do watch Salo.