Joshua Oppenheimer's daring feat is a documentary unlike anything ever done. Despite it being one of the most difficult things to watch for any human being (or because of it), The Act of Killing received praise across the board, including an Academy Award nomination. Without Oppenheimer's efforts, you might have never heard of the unspeakable events that happened when, in 1965-66, Suharto overthrew the then-president of Indonesia and a gangster-led death squad killed almost a million people. Did they pay for their crimes? Quite the contrary: said gangsters went on becoming political mainstays in modern-day Indonesia, are still now heralded as heroes, and admit to all these crimes with a smile and not a hint of regret. The gruesome twist of this documentary is that Oppenheimer asks them to re-enact the killings in surreal, sadistic snuff movies inspired by the murderer's favorite action movies. You are forced to stand idly by as they re-create brutal mass murder and joke about raping a 14-year-old. However, somewhere amidst this terrifying farce, the killers, too, have fleeting moments of realization that what they're doing is wrong. If you make it through this in one piece, try watching its more victim-focused follow-up The Look of Silence. Bone-chilling but very powerful stuff.