Event Horizon
Still one of the most effectively scary sci-fi/horror films ever, Hollywood is dropping the ball by not releasing a prequel. Imagine following the original crew as they test out the Event Horizon and end up in hell. That storyline deserves to be fleshed out (no pun intended).
The vast amount of possibilities that could be done with a film like this truly boggles the mind. It could end up being the perfect marriage of gore and mindfuckery.
