32. Sherlock: His Last Vow (2014, TV)
IMDB score = 9.3/10
Holmes and Watson? = Benedict Cumberbatch and Martin Freeman
Synopsis = Sherlock goes up against Charles Augustus Magnussen, media tycoon and a notorious blackmailer.
Defense by Paul Thomas Miller:
This is the BBC Sherlock episode which featured their version of Charles Augustus Milverton. Renamed Charles Augustus Magnussen, they really pull off the slimey, cold, evil of the master blackmailer better than any other adaptation I have seen. Magnussen makes my skin crawl the same way that Milverton did in the ACD story. I think they did this by stirring a big lump of Rupert Murdoch into the, already terrifying, character.
The main plot is a good remix of CHAS, but there are loads of other canonical elements too. The episode kicks off with Watson going to a drug den to rescue Isaac Whitney and running into Holmes on a case. This reworking of the start of TWIS is done perfectly: fresh and faithful at the same time. The maid Sherlock seduces in the original CHAS is replaced with a P.A. for exactly the same purposes.
In short, it's more canonical than you may remember it being and it certainly an enjoyable yarn.