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:
Comment fic (for wordstrings' holiday meme) by
rabidsamfan John knows what Sherlock would like best for Christmas. The author describes this as "fluff," and it is a little on the silly side, but not pushing the bounds of reality so far as to make it crackfic.
Holmes-Breaking by
loveslashangst John attempts to cure Sherlock of his more exasperating habits by treating him like a cat. The results are both entirely predictable and completely unexpected. This fic is laugh-out-loud funny. (M/M, explicit)
The Stand-Up's The Thing by
flecalicious Does reccing humorous fic about humor qualify as meta-reccing? John defends his sense of humor, and ponders Sherlock's.