Scrivener of Doom
Adventurer
I have to go with a few.
Caverns of Thracia because it made a dungeon into something truly 3D and, for me, defined what it meant to explore and investigate a location in D&D.
Keep on the Borderlands because it broke the megadungeon into smaller dungeons and that's something that my players prefer.
T1-4 Temple of Elemental Evil because it introduced vapourware - it took 6 years to release - and bait'n'switch advertising - there was little that was elemental about the dungeons and the bloody thing was incomplete - into D&D.
Caverns of Thracia because it made a dungeon into something truly 3D and, for me, defined what it meant to explore and investigate a location in D&D.
Keep on the Borderlands because it broke the megadungeon into smaller dungeons and that's something that my players prefer.
T1-4 Temple of Elemental Evil because it introduced vapourware - it took 6 years to release - and bait'n'switch advertising - there was little that was elemental about the dungeons and the bloody thing was incomplete - into D&D.