4. Spawn
Given that Spawn is about a soldier who is brutally killed and then returns as a leader of Hell's army, it absolutely, positively should be R-rated, but the smart cookies at New Line Cinema tried to force it as a PG-13, and the result was moderate commercial success and a critical drubbing. The film was lamented for its general goofiness, a result of the source material having to be watered down, when it's clear to most involved now that the only option is to go R. When talking about another Spawn movie, creator Todd McFarlane noted that it would be a standalone, R-rated story, much like The Departed. With Michael J. White keen to return in the titular role, and McFarlane's promise that it would "push NC-17", there's plenty of potential for this to be the Spawn film we wanted the first time, though most remain doubtful that it will ever materialise (despite McFarlane's insistence than an Oscar-winner, believed to be Jamie Foxx, is interested in starring).