MY TIME HAS COME. This is the best question I’ve ever received.
“Holmes & Watson" by Lee Eric Shackleford. I am in a one-person fandom of this play. It’s decently plotted and written but the depth of love and pining and desperation they have for each other is life shattering. It’s the best reunion ever written. It’s not available online. You can go through my Lee Shackleford tag if you want to know more.
“The Adventure of the Laughing Jarvey" by Stephen Fry. It’s a holiday pastiche. It’s so cute!!! They are such babes!!! Plus that bit where watson is like "i was decorating the house with mistletoe": I see you.
“My Dearest Holmes" by Rohase Piercy. This one is explicitly gay. The reason it’s not at the top is like…once or twice they are out of character but so are Doyle’s Holmes and Watson tbh. I can’t think of this pastiche without wanting to rip my heart out. It is excruciating. I mean just: ‘Did you think I was anything other than destroyed already?…Did you think that I cared for my reputation, when one word—one note, one token, could have let me know, oh God, that you were still alive? How could you, how could you, when you knew—that I loved you?’
“The Private Life of Sherlock Holmes" by Vincent Starrett. Does this book need any introduction? It’s mostly non-fiction essays and then one pastiche. Everyone who has a heart needs to read this.
“A Study in Emerald" by Neil Gaiman. This has so much hidden from the audience that it begs its own fanfic. (I’d recommend reading A Study in Midnight at some point afterward for the true gay version.)
"The Seven-Per-Cent Solution" by Nicholas Meyer. This was extremely popular in its day and perhaps the most successful pastiche. Watson takes Holmes to Vienna to see Freud to cure his addiction. It’s not my own favourite but it’s good and A Classic.
And there are many more! Those are just what come to mind first and/or are my most treasured.
For the final (maybe blasphemous??) truth. Holmes fanfic is overall better than Holmes published pastiche and many fics ARE pastiches and done even better than published versions because they are written by really dedicated fans. If you haven’t read these yet try them out.