Author has written 1 story for Harry Potter, and Fate/stay night.
I am 25, male, and working as a high school science teacher in Europe for a couple of years before I head off to graduate school to get a masters degree in meteorology. I have yet to decide my specialty, it will either be tropical weather (with a focus on hurricanes), severe weather, or climate. Unfortunately, with the imminent inauguration of Trump the idiotic climate change denier, it is likely he will slash funding to all climate scientists, I may have to avoid that specialty.
Harry Potter and the Eclipse Princess: A Harry Potter/Nasuverse story that (for now) focuses on various Type-Moon characters making a mess of Harry Potter cannon. 10 chapters are mostly complete (some editing is required). I was far too busy with being a new teacher to write for the past few months but have finally started again. Chapter 6 needed a lot of work, but will hopefully be finished in the next week.
I may also write a One Piece story at some point. I have some good ideas but will be focusing on the HP/Fate story first.
Fate/Stay Night- This one is really fun and is very complex. Great potential for good stories, From Fake Dreams is the best. I still need to play the VN, it is sitting on my computer downloaded but I only just passed the prologue (and that was months ago).
Naruto- While I am not too fond of canon (it eventually became shark-jumpy), it is a great sandbox for fanfiction. There are a number of interesting stories and many ways to approach this world. There are even more crap stories, then again 90% or more of everything on this site is crap (badly written, terrible grammar, boring/uninteresting/strictly canon). There are many great stories to be found, but A World Full of Monsters is one of the best.
Bleach- This show started out so well, and has been slowly dying ever since. I finally caught up by reading the last 30 chapters and basically nothing has happened! What the heck is up with how powerful the Quincy dudes are anyway? The power creep in Bleach is terrible, it should be more like Hunter x Hunter when it comes to power. Instead of the whole "power levels" type DBZ thing, skill should be far more important (see: Hisoka. Odd skills with apparently little direct combat applicability, stupidly strong). When will it finally end? Still the characters are interesting, their designs great, and powers quite varied. Great fanfiction potential, but there have not been too many good Bleach stories written recently.
Highschool DxD- I'm not sure what it is about these stories, but I quite like them. I've never watched the anime and have only read the first few light novels (through the Phenex arc), but there are some really good DxD stories out there. My favorite is A Demon Lord's Hero (also a Fate crossover which makes it even better).
Worm- I am really enjoying reading the various stories that this fandom is producing. There are not a lot of them, but they tend to be of surprisingly high quality. I need to actually read the source material at some point.
Harry Potter- There is so much written for it that some of it has to be great (and some of it is). As a children's story HP is amazing, when viewed critically it falls apart at the seams and there are so many ways to fill in those holes and change things.
One Piece- My favorite anime/manga, but not my favorite fandom. Most One Piece stories just lack something. Perhaps it is because the source material is already so good so fan fiction looks bad in comparison. There are some good stories but I wish the One Piece writers would try a bit harder. Rehashing canon with an extra character or two is not fun- if you are going to change things by adding additional main characters there should be increasingly significant deviations over time. Following canon to the letter is not only boring but also bad writing. The story This Bites! does what I want to see in One Piece stories brilliantly. It may be following Luffy's cannon journey for islands visited, but there are some massive deviations because of the crazy, quirky, and fun Cross & Soundbite duo.
My Hero Academia- This is a manga I discovered recently and it is great (Tsuyu is best girl)! It has an anime now and hopefully that will bring it to the attention of a wider audience. There are a full 23 stories right now (up to 230- hooray!), but it has the potential to become one of the better Shonen series (replacing the dead-but-not-really-because-side-stories-and-endless-anime-filler Naruto as one of the "Big 3"?) Hopefully it will gain a strong following and some quality fanfics will be created- it should be an excellent sandbox given the wide variety of powers displayed and huge cast of characters.
RWBY- I still haven't watched all of it (am half-way through season 2) and I really should, but these stories tend to be quite good. Too many fem-slash pairings for my liking though (but with only one real male option- Jaune- it is completely understandable).
Others: One of the best stories I have ever read, other than everything Gabriel Blessing has written (I hope he starts writing again, it has been 2 years), is Embers, an excellent Avatar: The Last Airbender story.