The Neo Geo was home to some of the most iconic arcade games of the '90s, and, like any other popular system, it saw more than a few unreleased titles during its lifespan.
One of the most elusive Neo Geo titles has to be Mystic Wand, an Alpha Denshi / ADK game which was in development very early in the console's life. The company was one of SNK's key software supporters, and created the likes of Magician Lord, Ninja Combat and World Heroes.
According to former Alpha Denshi staffer Hatono Takashi, it was developed between 1990 and 1991, and contains action and puzzle elements; the gameplay was based on Tecmo's Solomon's Key. The planner was Kenji Sawatari, (World Heroes creator), while the designer was Gen Suzuki.
Takashi told Neo Geo Protos that:
The location test was held at a game center in the town of Okegawa. The income was good on the first day, but after that it dropped sharply, and no matter how many times I made adjustments to it, the income did not go up, and so as a result, the game died. And since it was a dead game, there was no catalog, panthlet, flyer, etc.
After that, Gen Suzuki hid the development board, and when he was dismissed from the company, it seems that he took it away (in the form of stealing from the company). If this game ever comes up at auction, the seller is him or someone who bought it from him.
What makes Mystic Wand so important to collectors is that, as Takashi says, the prototype board hasn't been preserved and dumped, making it one of the Neo Geo's 'lost' titles.
You can see more of the game in this excellent video by The Basement Brothers.