What was your hardest rom to find?

Im bored and I was thinking what was your hardest rom to find and how long. For me it was the illusive powere instinct matrimelle. I dont know why but most were fakes and maybe it was the newest game snk put out in a long while. The others flowed like water but the elusive pim was really difficult to find. Took me a month to find reall game and dat. Any others?