So, this has long been an interest to me. Truly true, ultimate exclusives. Games that were only ever released in one place, ever. Never ported, never revived, never revisited, never re-released. Games that appeared one time, in one place, and outside of emulators (which DO NOT COUNT in this), can only be played on one platform, ever.
So, I'm looking for games like Uniracers, in essence. It was released on the SNES, and never released anywhere else, and will likely never be released anywhere else, including Nintendo's Virtual Console because a lawsuit with Pixar put an early end to the game. It is an exclusive in the truest sense of the word. It exists in one place, on one platform.
If there are enough good posts to this, I may keep an update of the first post with a list of all titles mentioned.