Saw

Adam and Gordon wake shackled at opposite ends of a filthy tiled room with a body between them holding a gun and a tape recorder.

James Wan and Leigh Whannell shot it fast on a small number of sets, with Whannell playing Adam, and the film's reputation as the beginning of torture porn is largely unearned: almost all of the violence is in flashback or off screen, and the film is a puzzle-box thriller.

The reverse bear trap in the opening is the design that launched everything.

Tobin Bell is on screen for very little and the character was written as a supporting part.

The last thirty seconds are one of the great final reveals in modern horror, achieved with a light bulb and a slow stand-up, and seven sequels have not damaged them.