Toughie.
If it's playing you're talking about, I suppose I'd have to say Chateau D'Amberville purely for the nostalgia trip- it was my very first adventure (ah, Naarg the Old One, adventuring Cleric- I ought to bring him back as an NPC someday). Other adventures all sort of blur together in my mind, I suppose because for 20-odd years I've been nearly always DMming instead.
Sure it's a disjointed mess when you read it, and pretty cooky and silly when playing it too, but when you're new to the game, none of that matters.
If it's DMming you're talking about, it's a much tougher choice, but I'm going to go with Gates of Firestorm Peak- the first time I really put a sense of wonder, awe, and even terror into the hearts of my players, and gave them an ending they'll never forget. I got a real feeling of accomplishment running it, too, since it's a large adventure and I pulled elements from Call of Cthulhu d20 to make it even weirder and more frightening.
Close runner-up for running, Tomb of Horrors- just watch the players squirm, particularly when they have some idea of the DC necessary to avoid the Soul Suck at the end and player after player keeps falling to it. Every roll has more tension than a suspension-bridge support cable.![Devious :] :]](http://www.enworld.org/forum/images/smilies/devious.png)
If it's playing you're talking about, I suppose I'd have to say Chateau D'Amberville purely for the nostalgia trip- it was my very first adventure (ah, Naarg the Old One, adventuring Cleric- I ought to bring him back as an NPC someday). Other adventures all sort of blur together in my mind, I suppose because for 20-odd years I've been nearly always DMming instead.

If it's DMming you're talking about, it's a much tougher choice, but I'm going to go with Gates of Firestorm Peak- the first time I really put a sense of wonder, awe, and even terror into the hearts of my players, and gave them an ending they'll never forget. I got a real feeling of accomplishment running it, too, since it's a large adventure and I pulled elements from Call of Cthulhu d20 to make it even weirder and more frightening.
Close runner-up for running, Tomb of Horrors- just watch the players squirm, particularly when they have some idea of the DC necessary to avoid the Soul Suck at the end and player after player keeps falling to it. Every roll has more tension than a suspension-bridge support cable.
![Devious :] :]](http://www.enworld.org/forum/images/smilies/devious.png)