Of all fanfic genres, humor might be one of the trickiest to write well. A decent humor fic that doesn't cross over into crackfic requires a keen understanding of both the characters in a fandom and what fandom finds funny about them.

( Three Sherlock fics to tickle the funny bone )

With a line like "I left my riding crop in the mortuary," is there any way that Sherlock fandom wouldn't have generated a subgenre of John/Sherlock stories with BDSM elements?

( Three delightfully kinky fics: )

Canon suggests that Sergeant Sally Donovan has an irrational dislike of Sherlock. She's presented as an unsympathetic character, and made the target of one of Sherlock's particularly cutting remarks in A Study in Pink. Fandom, however, has produced more nuanced views of Sally.

( Three glimpses inside Sally Donovan's head: )

Molly Hooper hasn't been given much in the way of character development by the writers of Sherlock. Fortunately, fandom is making efforts to fill in the gaps.

( Three takes on our favorite pathologist: )

Sherlock fandom has produced some very interesting what-if-John-and-Sherlock-were-born-the-opposite-sex fic.
( Three versions of Sherlock and John as women: )

Growing up Holmes must have been a unique experience, if Sherlock and Mycroft's interactions are anything to go by.

( Here are three takes on the possibilities: )