Most of my DMing was done back in the day, when I would run the neighborhood kids and a few schoolmates through various adventures. To that end, I am choosing B1 - In Search Of The Unknown as my favorite adventure to DM. You could stock the dungeon with any number of critters, loot, junk, and random encounters - and never do it the same way twice! As a novice DM, it really grabbed my attention.
Honorable mention goes to B2 - Keep On The Borderlands. Excellent low-level crawl. The owlbear always got their attention, if they felt a little too cocky after knocking off some kobolds.
I would be remiss if I did not give a shout out to T1 - The Village of Hommlet. I don't think I had the proper DM chops to really give this the full experience it deserves back then, but now I have to consider it my all-time favorite low-level AD&D module. The suspense slowly builds up starting in Hommlet, and gets bumped up a few more notches exploring the creepy moathouse (frogs, spiders, and green slime, oh my!). By the time the party reaches Lareth the Beautiful, the tension is so thick you need a vorpal to cut it.