Over at GameSniped, Castlevania4ever is selling his massive collection of prototype and unreleased games! If you are interested in buying any one of them, just send him an offer through a PM on the GameSniped Forums.
His collection spans over several different systems, including Gameboy, NES, SNES, N64, PS2, Genesis, and more! It’s really a huge list, so go check it out! There are some very rare items on the list, like the NTSC NES version of Earthbound, or the unreleased N64 game Toon Panic. I tried to buy Toon Panic, but someone had already offered over 1000 USD, which is way out of my price range. So if you have some money to spare and you buy one of his games, you can help build Unseen 64’s archive by providing us with pictures and video of your purchase!