I am sondrex76, I design a fantasy universe in my free time, have a tendency to point out misspellings and such in the fanfiction I read and am on my second year of university for a bachelor in game programming. I have yet to write any fanfiction(except the one time I did, but I were young(er) and that thing were an eldritch abomination that have been deleted long ago) and probably never will, whenever I write something it tends to be something related to my fantasy universe rather then something someone else have created(though many scenarios have been outplayed in my mind, most of them involving OC's from my universe and random circumstances in various fandoms)
I have read a ridiculous amount of How to train your dragon and Harry Potter fanfiction.
If you are looking for a good HTTYD fanfic I recommend Nightfall and its squeal: https://www.fanfiction.net/s/10509381/1/Nightfall
If you are looking for HP fanficitons I recommend "Lily and the art of Being Sisyphus", the author has written numerous other fanfiction in the same multiverse and/or universe and the whole concept are rather interesting, it's a MoD fem!harry fanfic, but it's really interesting: https://www.fanfiction.net/s/9911469/1/Lily-and-the-Art-of-Being-Sisyphus
I would also recommend "A Black Comedy": https://www.fanfiction.net/s/3401052/1/A-Black-Comedy it is hilarious and just awesome
"Princess of the Blacks" and its sequels are also quite awesome, however the main character is not a good person, and it is really dark, at least in some places.
Of course I can't forget about "Harry Potter and the methods of rationality", it is the best fanfiction I have ever read and simply cannot be beaten as far as I am aware(though I would love to be proven wrong)
I have also read some My hero academia fanfics, and among them "Something borrowed", an ongoing fanfic, is somewhat interesting: https:///works/13918209/chapters/32032938