This one's a fairly recent acquisition but I'm really interested in seeing if anybody else has even heard of it.
Nightmare/Atmosfear: The Board Game

I found it at a city-wide garage sale about a year ago for about fifty cents. According to the literature it's the very first board game to include VHS "technology". Basically the video is a timer that runs for an hour and periodically you're interrupted by the Gatekeeper:

who issues you tasks and such.
It's really cheesy fun, but what really interested me was when the tape ended and there was a trailer for Nightmare II: Baron Samedi
Apparently according to this:
http://en.wikipedia.org/wiki/The_Gatekeeper
there's been thirteen games for VHS, DVD, PC, and card formats, there's a mobile version in the works, and there's a television series in development. There's links at the bottom to message boards and all sorts of stuff.
For a game that looks like it was produced in somebody's basement for shits and giggles it apparently caught on in some market.