First gaming magazine you ever bought.
One day at the book store, having been disappointed that there were no new D&D books to be had, I decided to take a chance on the latest issue of Dungeon magazine instead. This was at a time that we were playing at least a couple times a week on average, so new adventures were about the most useful things I could ask for. The magazine didn't disappoint. Featured on the cover was an adventure set in a theater, titled Legerdemain, which unfortunately I never did find a good time to run. Nevertheless, it was a good read with a lot of thought-provoking material, and shortly thereafter I filled out the subscription card folded in the middle.
Almost every issue had one or two adventures that I could use, mostly AD&D 2E stuff that was easy enough to convert to classic D&D. Nearly all of it was at least entertaining to read, even the ones that just did not fit my campaign or personal DMing style. A lot of it was pretty railroady, because this was the age of plot-driven adventures, after all. Even so, quite a few authors managed to make an engaging backstory while leaving plenty of wiggle room for player and DM improvisation. Even the irredeemable railroads could be mined for locations, NPCs, and other bits and pieces.
It took the advent of 3E to get me to let my subscription lapse.
I was considerably less impressed with the only issue of Dragon I ever bought, a couple years later.