Eternal Darkness: Sanity's Requiem (GCN)
Took me forever to find a used copy since it was so rare. Found one at GameStop, the case looked like crap but I was like, I need this. Surprisingly, I haven't even beaten it lol
Zelda: Collector's Edition (GCN)
Got it with that GameCube bundle but man, did that game become ever so rare after the promotion ended. If you can find a used copy, it costs like $45. And Zelda: OOT/Master Quest. Took forever to find that too.