These were all bitterly disappointing, but collectors of such things occasionally speak of one thing that wasn't - a novelty sold for just one year that worked EVERY time, and which no-one ever found out how it worked.
That item was The Inexplicable Thrift Store Find. The effect is simple and bizarre - five cards are mixed, a dice rolled and a random card counted to - this sets off a chain of actions that leads to an impossible prediction that they will be utterly unable to explain. The Inexplicable Thrift Store Find is perfect for presenting a real mystery that seems totally self-contained. The effect comes with all the props as well as a downloadable pdf and a video explaining the method and presentation.
Inexplicable Thrift Store Find was previously available under a different name, so if you bought it under that name, don't buy it again unless you REALLY WANT TO.