I think Saw is an excellent idea, think of the great modes you can have and if you fail showing gruesome dismemberment on the new color dmd display the size of WOZ. Make TFTC look like a choirboy.
But if memory serves, I think all the horror related pins done had a big humor element to it, the marketing boys probably figuring a real horror pin wouldn't go over well with people at bars wanting a good laugh. Though I haven't played Freddy.