1. A3 Assault on the Aerie of the Slave Lords (1981)
The gnoll dungeon is okay, but what makes this module fascinating is Suderham, the City of the Slavers. Suderham is delightfully wicked. But wait -- you get two dungeons for the price of one! And what a climactic battle!
2. S4 Lost Caverns of Tsojcanth (1982)
It seems like the perfect blend, with an exotic (gnomes were exotic back in 1982) "home base" for character aid, wilderness setting with a whiff of political intrigue, an exotic dungeon (with Arabian motifs), planar gates, and a host of new monsters in a fat preview of the Monster Manual II. A classic I used to enjoy running or playing over and over...but the last time I ran it recently, the first level of the dungeon felt too random and surprisingly dull. So sad it didn't age better...
3. T1 Village of Hommlet (1979)
The dungeon is good (if not overly deadly on the lower level), but this is better known as the first published village provided in intricate detail. It's a setting you will want to revisit well after the dungeon is cleared out.
4. EX1 Dungeonland (1983)
Not only a fun adventure, but one of the first that had a plot that included scenes and not just encounter areas. The opportunities for hilarious role-playing are almost endless. The scenario has some nice twists at the end that still hold up well all these years later.
5. I6 Ravenloft (1983)
Gygax’s flavor text had brought mood to the setting before, but never in the way that Ravenloft just dripped with Gothic flavor. Strahd von Zarovich was a character who felt so real, I assumed back then that he was a character from literature (and was him for Halloween one year!). The 3-D castle maps are a treasure.
6. B5 Horror on the Hill (1983)
A great combination of wilderness and dungeon. Each dungeon level has a unique identity. If the module had not glossed over a "home base," this module would have scored even higher for me.
7. G2 Glacial Rift of the Frost Giant Jarl (1978)
The first dungeon that really used the environment itself against the PCs. Never mind the frost giants -- just watch out for the icy ledges!
8. T2-4 Temple of Elemental Evil (1985)
The first “super”-module. The Temple was just amazingly big! There are opportunities for role-playing, interacting with competing factions, and planar exploration -- but these factors are clearly subordinate to hack n' slash as written.
9. B4 The Lost City (1982)
The first indoor sandbox campaign? Much like Temple of Elemental Evil could have been, Lost City’s strengths are its size and its competing factions. Its weakness is its implausible ecology (of course, most dungeons didn't make sense back then), but it remains fun to play.
10. X4 Master of the Desert Nomads (1983)
A great, story-driven wilderness adventure. The wilderness part is great, but the dungeon at the end is practically an afterthought.
11. B3 Palace of the Silver Princess (1981)
The fact that the dungeon doesn’t seem to fit inside a palace only adds to the weirdness that pervades this module. Still, this is weirdness in a quirky fun way.
12. B2 Keep on the Borderlands (1981)
Ninety percent of the dungeon is generic as can be, but this is still the quintessential mix of village, wilderness, and dungeon served as a self-contained universe for a mini-campaign.
13. A2 Secret of the Slavers Stockade (1981)
One of the earliest dungeons that made sense, the Stockade is an early masterpiece of dungeon ecology. At the same time, fighting hobgoblins over and over did get old after awhile.
14. EX2 Land Beyond the Magic Mirror (1983)
Not as much fun as its predecessor, but the second “Dungeonland” module was still a treat and for much the same reasons. Not just a scenario, but a mini-campaign setting, if your characters wish to stick around...
15. G1 Steading of the Hill Giant Chief (1978)
One of the first early dungeons to imply that monsters were not static, but ate, slept, etc. Though a cake-walk for the party levels recommended, it is a good adventure for mid-level characters.
16. DL1 Dragons of Despair (1984)
An epic first try, with mixed results, at trying to cram a huge campaign setting into one module. The maps are neat, the dungeon has its moments, and draconians are, well, cool.
17. “Baba Yaga’s Dancing Hut” (Dragon, 1983)
Roger Moore's answer to every player who wrote Dragon magazine demanding tougher dungeons. This menagerie of every tough monster there was in the rule books circa 1983 was designed as a meatgrinder for hack n' slash characters. I always wanted to use it.
18. UK6 All That Glitters… (1984)
A treasure map, a plot that tied the dungeon settings together, and exotic locales across the World of Greyhawk (though altered in names). This was dungeon crawling meets pulp adventure.
19. “The Twofold Talisman: Part 1″ (Dragon, 1983)
A fun, funny little gem from Dragon magazine that I had a great time with back then.
20. “Citadel by the Sea” (Dragon, 1982)
Good dungeon design (possibly the first where it mattered how pure the dungeon air was) and an interesting plot has brought me back to this adventure time and time again, but this is a scenario that needs a "home base" for characters and, curiously, at no time that I've run it has any group ever finished it.