At the 1998 NBA All-Star Game, fans received discs with the demo for a PlayStation game called NBA 2-Ball. The game was pretty bad - possibly defective - but it's extremely rare. So a surviving copy may be extremely valuable.
A New Jersey man provided pictures of the disc to a blog that a while ago had written about NBA 2-Ball, which runs on "the awful NBA Jam Extreme engine," so it wasn't much fun to gamers, and was utterly useless to those without a PlayStation. Most folks threw the discs away. Only two copies were known to survive as of a year ago, one of them cracked in two. This New Jerseyan would seem to have a third.
He's going to put it up for sale on eBay, where as we've seen before, very rare games have commanded five-figure bids. I haven't seen it listed there yet. Of course everyone is immediately skeptical of its authenticity, but the guy has answered all questions asked of him and provided as much visual proof as he can. So who knows?