The idea of a Grand Unified D&D has me thinking about adventure modules and how they epitomize play and serve as a powerful shared experience for otherwise disparate gamers.

So, what are the truly defining adventure modules for each edition of D&D, in your opinion? Which ones exemplify the strengths of a particular edition, as well as serve as a common touchstone for that edition. And, assuming a "universal edition" is even possible, which ones should be repackaged for D&D Next to help create an adventure foundation for the new game?

My choices include Keep on the Hinterlands and Isle of dread for Basic/Expert D&D, Temple of Elemental Evil for 1E, and Forge of Fury and Red Hand of Doom for 3E. I can't think of a single defining adventure for 2E -- I never ran modules when playing 2E -- and I am not familiar enough with published 4E adventures to judge.