D&D acid house. Awesome.
A buddy and player in my group bought this and its sequel and worked them together into a single adventure. We then devised a set-up whereby I would TPK the group and have them wake up in the shaft tumbling into Dungeonland, which my buddy would then run (allowing me to play my ubercool fighter for a while).
I ran the party through
Ship of Horrors and wasted them with unfettered glee. My buddy Andy joined in the fun by offing a few rival PCs into the bargain before finishing himself off. There are times when it is very good indeed to be a DM. While the other players sat there in shock, Andy and I swapped places - I busted out Ubercool Fighter (he was 12th level by then) and Andy took the spot behind the screen. More priceless expressions from the other players.
Andy (at the time a psychology student with a deep fascination for serial killers) unleashed all manner of demented hell upon us. The fact that everyone we met seemed to be clinically insane in one way or another freaked the entire group more than the Ravenloft game that had come before (who cares about limbless zombies when the house is trying to eat you?). We tried hard to keep our wits about us, up until the tea-party. My ubercool fighter ended up wearing the mad hatter's hat and prancing naked through the grass and I'm not too sure what the rest of the group were up to, but it soon came to blows. We decided that we were well out of our league and were going to take no nonsense. Or prisoners. Or even very much time.
I spent most of the rest of the session under the influence of haste spells (having a potion of longevity in by bag helped) - ubercool fighter became ubercool blender. I did for the mimic in three rounds, the behir took two, the queen of hearts took two rounds and I made furry chunks of the white rabbit in one round, before the poor guy could even open his mouth. If it looked like it came from a fairy-tale, we attacked it. If it spoke or moved, we attacked it. Heck, after the mimic, we weren't even picky about that either. It became this dreadful excercise of psy-ops warfare, with us feeling like we were fighting a guerilla war against an enemy who would rather derange us than kill us.
We eventually made it out, iirc, by animating a dead party member as a zombie and using him to activate some kind of exit gate. Don't remember that bit too well, actually, as we were mostly engaged in furious arguments with the player of the now-zombified character. The plan, unfortunately, involved leaving the zombie behind and the player was, well, less than content with that as a fate for his heroic and dashing thief. Tough nuts, as they say.