Last night I had the chance to play my first session of Dungeon Crawl Classics (I'll talk about it at greater length tomorrow) and I had a blast. As I said then, DCC RPG is a game that really won me over, despite my initial skepticism, because it was clearly not written to be a mass market crowd pleaser. That is, it's not a "generic" fantasy game, but instead comes with all sorts of mechanical, esthetic, and gaming cultural (e.g. the coolness of Zocchi dice) assumptions that not every gamer is going to share -- and indeed many will actively dislike.
Despite, I think DCC RPG is a great game. Indeed, I think much of its greatness comes from the very fact that it was designed with a niche audience in mind rather than a broad one. So, my question for today is this: what is your favorite "niche RPG?" By this, I mean a game designed for a small, specific audience that understands and appreciates its quirkiness in a way that a mass audience never could.