OK. Caveat, I write crossovers.

Redisovery (ST:NG/Harry Potter)

https://www.fanfiction.net/s/6972218/1/Rediscovery

Flight of the Vigilant (ST: ENT/ Blakes' 7)

https://www.fanfiction.net/s/13466183/1/Flight-of-the-Vigilant

Old Game, New Players (ST:NG/Babylon 5)

https://www.fanfiction.net/s/13624854/1/Old-Game-New-Players

Requiem in Stellaris (ST:NG/Doctor Who/ Harry Potter/MCU/Darksiders)

https://www.fanfiction.net/s/13710261/1/Requiem-in-Stellaris

Though referenced in various tales (more specifically as the great-great-great-great-uncle of Hermione Granger Weasley) Sherlock Holmes appears directly in only one story:

The Adventure of Mr White and Mr Black (Sherlock Holmes/Watchmen)

https://www.fanfiction.net/s/13435760/1/The-Adventure-of-Mr-White-and-Mr-Black

Let me know what you think.