6k+ Harry Potter and the Natural 20 » by Sir Poley Milo, a genre-savvy D&D Wizard and Adventurer Extraordinaire is forced to attend Hogwarts, and soon finds himself plunged into a new adventure of magic, mad old Wizards, metagaming, misunderstandings, and munchkinry. Updates monthly.
Harry Potter & Dungeons and Dragons, T, English, chapters: 74, words: 314k+, favs: 7k+, follows: 8k+, updated: 8/2/2018 published: 5/7/2012
10k+ Harry Potter and the Methods of Rationality » by Less Wrong Petunia married a biochemist, and Harry grew up reading science and science fiction. Then came the Hogwarts letter, and a world of intriguing new possibilities to exploit. And new friends, like Hermione Granger, and Professor McGonagall, and Professor Quirrell... COMPLETE.
Harry Potter, T, English, Drama & Humor, chapters: 122, words: 661k+, favs: 28k+, follows: 20k+, updated: 3/14/2015 published: 2/28/2010, Harry P., Hermione G.
123 Trust in God, or, The Riddle of Kyon » by EliezerYudkowsky In their third and final year at North High, Kyon confronts the implications of the Riddle of Epicurus for his relationship with Haruhi.
Haruhi Suzumiya series, T, English, Drama & Spiritual, chapters: 2, words: 10k+, favs: 491, follows: 156, 12/17/2009, Kyon, Haruhi S.
43 The Finale of the Ultimate Meta Mega Crossover » by EliezerYudkowsky Vernor Vinge x Greg Egan crackfic. This was supposed to be a bit of utterly deranged fun, but got out of control and ended up as a deep philosophical exploration.
X-overs, M, English, Sci-Fi & Humor, chapters: 3, words: 13k+, favs: 93, follows: 45, 9/20/2009
19 Cold Comfort, but Cheap at the Price by Ukyou Kuonji Itoshiki-sensei, for all his despair, could take comfort in the fact that he is never alone, thanks to Matoi Tsunetsuki. On the other hand, she's not really that much help, especially with the ideas SHE comes up with...
Sayonara Zetsubo Sensei, T, English, Humor & Angst, words: 983, favs: 30, follows: 6, 3/21/2008