7. Paranormal Activity
It's crazy to think that horror phenomenon Paranormal Activity (2007) cost only $15,000 to make, but it did, and despite the incredibly low cost of the film's production, it made nearly $200 million at the worldwide box office, spawning a widely imitated and madly popular horror franchise in the process.
In hopes of creating a horror film more grounded in reality than the blood and gore of other modern horror flicks, writer-director Oren Peli filmed the whole thing on a home video camera. Because of this simple creative decision, the film didn't use a camera crew over its short, seven-day shoot. Peli also didn't write a script, instead giving the actors an outline of the story and allowing them to improvise in order to get a more naturalistic narrative.
All of this paid off, as the critical and commercial reception for the film was outstanding. With its gritty realism, disturbing imagery and skin-crawling tension, it remains even today a horrifying viewing experience, and arguably the best of the franchise.