I saw this thread, my fingers itched and I joined up just to reply. Unfortunately someone scooped me on my favorite old article, but here are some of my favorites anyway:
1. Chi-square test. I would like to know how many people became interested in math or science because of this little guy.
2. Tuckers kobolds. Having had to face a bunch of the little lizards based on this article, I will never forget...
3. Giants in the Earth. Always enjoyed these.
4. There was an article about artifacts based on real world items. Or did I dream it...
In general I always enjoyed new monsters, magic items or character classes. Crunchiness all around. I have only read one of the fiction stories, EVER. And that was the recent George R. R. Martin preview. Just an automatic skip for me.
Special mention for me was the Dragon annual with the gold cover. Everything in there was great!
This thread is reminding me of all those old mags buried in a box, a thousand miles away from me, sigh...