A "funhouse dungeon" is one where questions of ecology, naturalism, or even logic take a backseat to presenting a good -- and fun -- challenge to the players whose characters are exploring it. Good examples of published funhouse dungeons are White Plume Mountain and The Ghost Tower of Inverness for those unfamiliar with the concept. Outside the old school community, I think it's fair to say that funhouse dungeons have fallen decidedly out of favor and, even among old schoolers, opinion is divided regarding them.
So, I'm curious: how do you feel about funhouse dungeons? Do you use them in your campaign or are they reserved for one-shots? Or do you never use them at all? Me, I'm not a huge fan of them, but I have used and enjoyed them. Dwimmermount isn't a funhouse dungeon by any means; there are, however, parts of it that have a funhouse vibe to them. I think that's my preferred approach: using funhouse dungeons to break up the mood of unrelenting seriousness to which I can sometimes fall prey. They're a reminder to me that fantasy gaming should, first and foremost, be, well, fun.