Any gumshoe game, probably something shorter than Nights Black Agents: The Dracula Dossier. If I set it in my own setting, I’d like to use Bubblegumshoe to do my own telling of “Tomorrow When the War Began” basically what happens if on the summer camping trip after your last school year, your country is invaded. I can’t quite tell how good Gumshoe is for homebrew settings however.
My other want is to run a worldbuilding game such as the quiet year, for the queen or microscope, hacked to set up a concise and thematic noir mystery inspired by fiction like Disco Elysium, The City and the City or The Nice Guys, with a rich and vibrant world that the players are invested in as they built it. I’m tempted to hack the bladerunner RPG by Freeleague for the actual police procedural afterwards.