I think one of my absolute favourite obscure fic genres would have to be Mornington Crescent fic and I've just been linked to rather lovely perfect example:

The Goodge Street Gambit and the Controversial Non-Holmesian Principle by definewisdom
Lestrade and John play a game of Mornington Crescent, Sherlock tries to work out the rules.I'm currently wishing I'd ( Read more... )