On Halloween each year I marathon horror movies that I've never seen before. I try to pick one long-running franchise and marathon all of them, or just a bunch of assorted movies if I can't find a franchise that can fill a full day that I'm unfamiliar with. This year I'm going to be watching all seven of the Saw movies back-to-back.
I saw the first one back when it first came to video, and I remember liking it. I've never seen any of the sequels, and I've heard very mixed things about them. Picked up all seven on Amazon in a single collection for $7, so I won't be too disappointed if I end up not liking any of them.
I doubt it could be worse than last year's Final Destination marathon, anyway.