Going straight for the forbidden knowledge, are we? Okay fine, I'll play your game, although I'm kind of an open book when it comes to hobbies and whatnot so we'll stick with the one that people usually don't know:
Remember that time back around 2009 or 2010 (honestly you'd think I would remember this) when, as the story goes, a bunch of randos on 4chan produced and released a visual novel?
I wrote one of the paths in that. If you got here from Twitter that's not a surprise but it is still the thing I think is still not widely known.

