20 Huge Horror Movie Hits NOBODY Expected

For an entire decade, The Blair Witch Project appeared to have caught lightning in a bottle, being an ultra-low-budget horror film that captured the public's imagination and went on to become one of the most profitable movies of all time. But in 2009, Paranormal Activity enjoyed a similar trajectory, as after drumming up buzz at festival screenings in 2007, the $15,000 found footage film was acquired by Paramount.

Even with added post-production costs - including shooting a new ending - Paranormal Activity still only cost $200,000 when it was released to just 12 U.S. cinemas. With such a small initial rollout and the film featuring only unknown actors, it seemed like it would offer a decent return on Paramount's investment and then swiftly disappear. But Paranormal Activity did anything but that.

Due to consistently sold-out showings and strong word-of-mouth online, Paranormal Activity's theatrical run continued to expand, resulting in it ultimately grossing an outrageous $194.2 million worldwide. It remains one of horror's greatest and most surprising success stories, kickstarting a franchise which has netted almost $900 million in total, on a combined budget of just $28 million.