Saw (2004) Link

Many fans missed it on their first watch, but Jigsaw’s identity was actually revealed early on. In a flashback at the hospital, you can clearly see sitting on John Kramer’s desk. The Legacy of the Twist

The film's ending remains one of the most iconic "gut-punches" in cinema history. It worked because it subverted a classic trope: the killer wasn't a shadow in the corner; he was the in the center of the room the entire time. Critics at the time, like those at Rotten Tomatoes , noted its nihilistic streak, but audiences turned it into a massive hit, grossing over $100 million worldwide. Saw (2004) - IMDb Saw (2004)

It was shot for roughly $700,000–$1.2 million . Many fans missed it on their first watch,

Created by James Wan and Leigh Whannell, the film was born out of pure grit: It worked because it subverted a classic trope:

The entire movie was filmed in just 18 days , with the central bathroom scenes taking only six days.

Because they couldn't afford a dummy for every scene, Tobin Bell (who played Jigsaw) actually lay on the floor in the middle of the bathroom for the entire shoot to save money. The "Hidden" Clue