Media so rare it's almost lost or was thought to be lost

Oh I know a couple of these things:
1. Air Raid for the Atari 2600: very few copies of it are known to float around of this Space Jockey hack & it's still very mysterious in its origins.
2. Red Sea Crossing, another Atari 2600 game: EPYScope made a whole video surrounding the history of this random game.
3. The English release of Puyo Puyo arcade: This one was so rare & mysterious that people thought it was a bootleg for years. TCRF has a good article on the game that includes the regional differences between the original Japanese version & the oddball English version. Jonii did a video on the 1st game which also has a section dedicated to this weird English version.
4. Get Muggsy!: This was a short cartoon released on DVD that was only available through the Muggsy's meadow kids club & is now insanely rare, but the cartoon itself WAS luckily posted to YouTube by TenPoundHammer.
5. Labyrinth: The Computer Game: LucasArts' first adventure game, albeit it's a graphical text adventure with moving parts.
6. Dan Whalen - Fly Me Away: Only about 190 viewers as of now, so presumably only about 700 people have known about this song before.
7. The Groovenians: A failed pilot that aired on Cartoon Network's [adult swim] block in 2002. How someone was able to find it without the [adult swim] screenbug is beyond my comprehension.
8. The Tool Street Gang: Another failed pilot, this time it seemingly never aired. Again, WHERE WAS THIS FOUND!?