I am trying to remember the name of the two booths at Gen Con that have the used RPGs.
One has the long rows of book shelves with games you can purchase multiple and then get some free. Lots of Palladium, L5R, etc at discount.
The other is a game store that brings in old AD&D modules, box sets, and collectibles. They are all on tall tables with boxes organized by D&D worlds, etc.