The VOIDRUNNER'S CODEX is LIVE! Explore new worlds, fight oppressive empires, fend off fearsome aliens, and wield deadly psionics with this comprehensive boxed set expansion for 5E and A5E!
Vaesen - it’s gorgeous, and I also enjoy the system and setting / lore.
Dungeon Crawl Classics: Lankhmar - I’m a sucker for Lieber, and the DCC artwork is pretty amazing.
RuneQuest - anything Glorantha related, really
Mongoose Traveller 2e
AD&D Greyhawk Adventures sourcebook
Don't forget the already-extant Advanced Fantasy rules, which give you AD&D classes / races expertly converted to maintain B/X power levels. I can't stress enough how well Gavin handled that.