The Fright Catalog's Dead Fred runs on two 12V battery and sports four separate motors that allow it to sense passers-by, rise up out of the earth and chase them, howling and growling and dragging its entrails behind it. It's $2650, so it's a little pricey for Hallowe'en, but that sum does compare favorably with the total cost of ownership for a pet dog or cat, so when the kids start complaining that they need a companion who'll follow them around and do tricks, this might be a good choice.
(via DVice)