Methods Of Rationality (fanfiction)
Harry Potter and the Methods of Rationality is a fanfiction by "Less Wrong" (actually a pseudonym of Eliezer Yudkowsky) which postulates that the orphaned Harry Potter has been raised by a scientist stepfather and now has the equivalent rationalist skill of roughly an 18-year-old Eliezer or thereabouts, i.e., massively flawed but still pretty darned impressive. Naturally the hero's challenges have been stepped up in difficulty as well.
It would be fair to understate that this fic has proven itself popular.
TV Tropes page here (warning, potential spoilers).
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