Even with all its flaws, I love running people through Tomb of Horrors.
A wild sheep chase
Alice is missing and The space between us, the latter being borderline LARP.
Both games are pretty intense with a huge bleed potential making them memorable experience.
I haven’t run many true one-shots. Not short, contained, focused, pre-written adventures. Usually I’m just cobbling things together (which is why I actually really love your books). But I’ve always wanted to play the We Be Goblins! series.
This is hard one because most of the one shots are just awful as they rarely include any guidance to how to run them in short of time. At least every one shot should include a guidance of how and which parts to leave out when time is running out.
So the best ones are usually systems designed for one shots without separate scenarios but assuming you are asking about those the most palatable one has been DnD 5e adventure Sarah of the Yellowcrest Manor from Candlekeep mysteries. The middle part can be pretty much skipped if the time is limited, there is at least some guidance on how to run it and the end dungeon is short and sweet.
I always maintain that the best oneshot is the one you cobbled together last night. Get a little weird, slap some stuff together, and let the players fly off the rails.