I was thinking that it might be fun to run a game in which the paranormal doesn't really exist (or at least as far as the player characters know). It'd involve a group of ordinary people (with paranormal professional jobs) as skeptics/debunkers who go around disproving frauds, hoaxes, and charlatans (ala James Randi). False psychics, "legendary" monsters made of plywood and paste, and "ancient" artifacts made in the garage last week would abound. It would focus around mystery-solving and scientific inquiry, but I would probably keep the (slim) possibility of real paranormal elements (psi, magic, and so forth) existing. I'd probably also throw several guys in ghost or monster costumes at the meddling kids, as well.
I'd let this debunking campaign go on for quite a while...then hit them with something completely, utterly horrible, something designed to drive their rational minds to the brink of insanity.
Come to think of it, it's probably better done as a Call of Cthulhu game rather than BtS.
