It's some sort of annual festivity, which means there can only be a Steam sale to match. If you're not too busy pouring boiling oil onto the damnable children who keep on turning up at your door and begging for candy while you're busy trying to watch the latest episode of M.A.S.H., you might wish to play a videogame which you've not paid much for. Over eighty games are in the sale, most of which have a scary theme and crazy-low prices. There are also quite a few zombie-related games, but we all know zombies are about as scary as a cat dressed up as Wolfgang Amadeus Mozart these days.
WARNING: Comic Sans is used on the Sale page.
My personal picks would be Atom Zombie Smasher, Amnesia, Lone Survivor, Stalker Call of Pripyat and Vampire Bloodlines, but you'll be wanting to look at the full list here. Some of the prices are indeed ludicrously low - there are lot for under two quid in there, and the Cthulhu Saves The World/Breath of Death pack even comes in at just 66p.
There's also something I've not heard of before called "Trains Versus Zombies 2." That sounds like the best thing ever, until I remember what happened with Snakes On A Plane.