My first game we started playing about 1980 or so, first module was Keep on the Borderlands. I remember DM'ing it, and being so overwelmed with the coolness of D&D as a kid i would spend time just making up maps and such of the actual Keep, buildings, rooms, encounters, and get really into it lol. Just the artwork on the cover of the module sucked me into the D&D world instantly.
Trying to remember modules i really liked. Earthshaker of course, a huge super giant robot construct? Yes please. The Drow and Giant module series of course, awesome. My favorite one was the Castle Amber, my group really went all out on that one and had some major fun. In the end I think one of the party was stoned, so we had to abandon him because there are major foes in different areas that we had to fight, and the last 2 party members split up, one had to fight a giant zombie attacking a castle and the other a wizard had to fight an alien in a tower or something. We triumphed in the end but it was like a grueling football game that we only won due to lucky dice rolls and abandoning all hope of actually winning. lol.