A really important item that somehow slipped through the cracks on my list, the Forgotten Realms Campaign Set is probably the most important campaign setting since Gary Gygax’s 1980’s World of Greyhawk. 

This came as a boxed set with a large map, some transparencies to measure distances and a couple of books, one meant for players (Cyclopedia of the Realms) and another for DM’s (DM’s Sourcebook of the Realms). With a boatload of information on the setting, NPCs, character races, the pantheon of gods and how everything works in this world, this would have been an invaluable resource for anyone adventuring in this setting.

This boxed set was so successful that it would keep being published with revisions and updates well into the mid-90 (when I would eventually buy my own copy). This would be the basis on which much of D&D would be built in following years and new editions and it’s just as fascinating to read through today as it was in 1987.