Hey there. Honestly, I was just bored and had a bit of spare time.
I currently have a few ideas for some fanfics, but I don't really have the time to write them myself. I'm putting this together rather quickly because I wanted to share these concepts—in case anyone else would like to take one and write a story based on the premise.
I'll list two for now, but if I come up with others—and I don't feel a burning desire to write them myself—I'll add them here.
1) *Fate* / *Harry Potter* crossover: Mages in London initiate a Holy Grail War, summoning Heroic Spirits from the *Fate* universe to grant their wishes.
2) Multiple Reincarnations / *Fate*: Seven individuals, reincarnated from different eras, become Heroic Spirits and are summoned into the same Holy Grail War.
3) *Hazbin Hotel* / *Helluva Boss*: I've never actually watched either show, though I've read a few fanfics—most of which were left unfinished. This gave me an idea: someone is reincarnated as Lucifer's firstborn (Charlie's older brother—not an incestuous pairing; there are already plenty of those out there). He ends up having to forcibly take over the governance of the Pride Ring after Lucifer retreats into his mansion and abandons his duties.
4) *Naruto*: I'm surprised I've never come across a fanfic where someone is reincarnated as an illegitimate child of Jiraiya. Knowing that "pervy sage," he surely must have had a fling with someone at some point. It would be interesting if this character were somewhere between the ages of Kakashi and Itachi—it would add some variety and fit better within the series' canon.
5) Crossover: The protagonist is reincarnated as a Sandman, or Morpheus (you can decide whether they're the same entity or not), and can only communicate with humans through their dreams. You could set this in any kind of world—fantasy, action, adventure, etc.—though I personally envision it taking place in a setting focused on everyday life with a supernatural twist. It's a solid concept, but I can't quite figure out how to flesh it out properly, so I'll leave it for someone else to develop.
6) Twilight: I was watching a parody/mocking video about *Twilight*, which made me want to check out some fanfiction for the series. Half of it is garbage, and the other half is mostly abandoned—so, I had an idea. What if someone unfamiliar with the story were to reincarnate into that universe as Bella's uncle, becoming a vampire hunter? He could show up in Forks toward the end of the first movie or the beginning of the second, acting as an agent of chaos and destruction—a true villain. That sounds a lot more interesting than seeing yet another harem fic, or one where the main romance is with Alice—as is always the case.
I had other ideas, too, but I can't recall them at the moment; besides, those are ones I intend to write myself once I finish one of the other stories I'm currently working on.
If you decide to use this idea, I'd appreciate a small acknowledgment in the synopsis. That's all I ask—well, that, and that the story turns out well and isn't abandoned halfway through!
Best regards.