In the first place, one of my very favourite adaptations of Sherlock Holmes is a series of BBC radio plays starring Clive Merrison as Holmes and Michael Williams as Watson. There's also a series of non-canonical pastiches made after Michael Williams's death where Watson is played by Andrew Sachs. If you know Fawlty Towers at all, yes that Andrew Sachs.
He's pretty good too. The plays are very clearly a labour of love, occasionally gently poking fun at the canon. Holmes is acerbic and impatient and brilliant, Watson is intelligent and capable, and the two of them have a wonderful chemistry and sense of banter. I adore these. A lot.
The series also has some of the most bizarre slashy moments ever. Mary Watson makes two
references to her husband being totally in love with Sherlock Holmes, once accusing Watson of marrying her under false pretenses because obviously his heart really belongs to Holmes, not her, and once on her death bed (it's strongly implied in these that she dies of consumption/tuberculosis, actually) where she bemoans the unfair deaths of herself and Holmes as "everyone you've ever loved, John." There's also a shared drug-fueled nearly-fatal hallucination which is represented on radio by Holmes and Watson chanting together the English translation of some Wagner that Holmes was quoting at Watson earlier: "Let us die, and never part, together for the rest of time."( Today, I relistened to The Adventure of the Blanched Soldier. )
Watson could do so much better.