For a brief time, Hasbro's official website checklist featured listings for two "Halloween Horrorcon Value Packs" that were to be Wal-Mart exclusives... which also likely explains why they were canceled. (Wal-Mart had taken a good half-dozen exclusives and released them more-or-less simultaneously, leading to a huge glut. A lot of other Transformers exclusives were canceled during the Universe era.)
In 2004, several test-shots appeared on eBay in a group, among them a snow leopard redeco of the original Beast Wars Cheetor toy. This, presumably, was to have been Nightprowler, as the other toys in the group line up with the names given for the two Halloween sets. The toy would have transformed from snow leopard to robot, with two guns, one being a water squirter. As he was to come in a "Vs." two-pack with the Predacon character Waspinator, it is presumed that he was to be an Autobot.