Artificial scarcity? The only one that comes to mind is diamonds and even that is supposedly over. Or is it?
There was one after involving large banks and such after the great recession. I think Goldman Sachs was one of the ones that got stink-eyed for it. They were buying up aluminum as fast as they could get it and warehousing it to create shortages to inflate prices on the London Metals Exchange where they were also very active players. I recall reading an article in I think Rolling Stone several years ago while sitting at a garage about the different big finance companies who were doing similar things with metals because it was such a poorly regulated part of financial markets.