My Sherlock Holmes / Potterverse story is up here. This all happens about a hundred years before Harry birth, so none of the characters from the HP books are alive yet (with the exception of Nicholas Flamel, but he’s not in it). It’s a sequel to Watson’s Task. I’ve rated this one T (teen) for a bit of gore (nongratuitous, I think) and attempted creepiness (attempted on my part; the character in question isn’t particularly trying). It takes place in late 1888, shortly before the Canonical Valley of Fear.
This one’s got all kinds of things I hadn’t done before, like actual original plot. Mystery. Dialogue and action. it’s been very educational, and would have been significantly worse without beta from synaesthete7 and batwrangler.