I had started some macros before 3e that I used to typeset adventures. It took care of room numbering cross-references, typesetting AD&D in a nice manner, dropping pics in at convenient places and indexing spells and magic items. It didn't do anything with stat blocks, though that was my goal.
Recently, a lot more have been standardized, like traps, the new encounter format, etc. So I'd like to see macros for that. Especially, I'd like to be able to define a character/trap/whatever in one format somewhere, and then be able to call a command which will insert a short statblock in one place, and a larger one elsewhere. That's what I was thinking of coercing BibTeX into doing, but never got around to it.