I apologize if I wind up repeating a lot of stuff that has already been mentioned, but then again, I hope it adds weight to the stuff that's come up before.
* Elemental Gods
* The Missing Dragons--Orange, Yellow, & Purple
* The Gem Dragons article (esp. mentioning their singular god-like dragon, the Ruby Dragon, IIRC)
* Guild of the Black Hand (August 1990 issue)
* The Last Call Inn (also from August 1990 issue)
* Roger Moore's articles on demi-human cultures & deities.
* The "Good Hits, Bad Misses" article/tables.
* The Winter Elves
* Giants in the Earth: esp. the Nodwick one, Beowulf one, & Ged/Sparrowhawk one
* Voyage of the Princess Ark, esp. ones which introduced new class options for OD&D (like the bard & half-elves)
* SnarfQuest
* What's New!
* Dragon Mirth (liked a lot of the Joe Pillsbury comics from that section)
* An article on the "other metallic dragons"--mentioned ones such as the iron dragon & vanadium dragon, IIRC
* (yet another) Article on dragons that introduced the Raindow Dragon & Gray Dragon (IIRC, also had the Cobra Dragon)
* An article that covered different materials for constructing arms & armor (back when the type of material used dictated how high of a magical bonus armor or a weapon could have)
And for some non-D&D ones (i.e., honorable mention):
* The Marvel Phile!
* The Eye of the Monitor series (IIRC)--basically reviewed various computer games, & the back part of the article was a Hints section submitted by readers (Man, did that ever help me with a couple of Ultima games)