Air Gear: Kuro no Hane to Nemuri no Mori - Break on the Sky

There are good anime that stop after one or two seasons despite the source material still having a lot of good ground to cover, much to everyone's disappointment. So we wait, and wait and wait... for nothing.

This list features a selection of notable incomplete adaptations that have stuck in the limbo for at least five years without any new announcements, in most cases far longer than that. For simplicity's sake, I will only include the chronologically latest entry in the series, not the highest-rated or most widely known. The notability guideline I'm using is roughly based on a combination of rating and popularity at the time of inclusion.

What this list DOESN'T include:
* any original anime;
* any inconclusively finished anime based on games, mixed-media projects, or any other non-written sources;
* adaptations with anime-original endings meant to serve as a conclusion to the series (I strive to verify every entry in this regard, but please do inform me if something has been added in error);
* incomplete adaptations of manga and LNs that have gone on long or even indefinite hiatuses themselves, leaving potential new seasons of TV adaptation without enough content (e.g. Hunter x Hunter, Nana);
* adaptations of officially discontinued manga and LNs, as it's obvious the publisher isn't interested in having them done;
* incomplete adaptations with anime-original endings that stop before the part of the source material that very distinctly made the series' fans unhappy (Usagi Drop is a good example).

I also reserve the right not to include adaptations with anime-original ambiguous endings if there is no greater overarching plot thread carried on in the source material, or if the source material also ends ambiguously without wrapping it all up. Those are low-priority items.

See also the counterpart to this list: NotLikeThis — anime-original sequels nobody wanted: https://myanimelist.net/stacks/2355.

List alumni:
* Slam Dunk – a new movie has been announced, which will presumably pick up where the previous adaptation ended and cover the last game in the manga, which is also its best part.
* Spice and Wolf — a whole new season has been announced! Woof!