The latest commercials for James Wan's haunted house picture The Conjuring (which opens nationwide tomorrow) follow a marketing campaign that's been used a lot lately for horror movies, most recently for Evil Dead. Along with clips from the actual movie, the spots feature reactions shots from test audiences, captured in green-tinted night vision and accompanied by enthusiastic tweets. Grown-ass men jump out of their seats. Their female counterparts cower. Others just sit there, motionless, eyes open, visibly shaken. They're reacting to Insidious director James Wan's latest creepshow as if it's the scariest thing they've ever seen.

Those are the kinds of physical reactions that only horror can deliver. It's not relegated to in-theater experiences, either—while watching films about ghosts, ghouls, slashers, and other inexplicable darkness, terror can be even more palpable when you're home alone, vulnerable to whatever might be lurking beyond the front door. It's a rush. That fourth wall makes you feel safe to enjoy the scares. Once the film's over, you're ready to quote that great '80s horror character actor Tom Atkins, from the 1986 cult classic Night of the Creeps: "Thrill me."

And no horror films have thrilled moviegoers more than the 50 scariest movies of all time.