...although, if you said that Castle Greyhawk (WG7) was your favorite, then I would be forced to hunt you down.
Hey, who doesn't want their PC to meet Asmodeus in a low level adventure?
This trainwreck of a mega module was my introduction to the world of Greyhawk, and can actually be pretty fun of approached correctly (and heavily modified and cleaned up).
I didn't learn of the modulus somewhat ugly intent and history (essentially as a middle finger to Gygax) until much later.