>Clark Ashton Smith
Three settings in general, Hyperborea: Pre-historic world with lot's of sorcerers and horrible Lovecraftian things fucking around.
Averoigne: Basically France province in Medieval times with sorcerers and horrible Lovecraftian things fucking around.
Zothique: Dying Earth-style, with sorcerers and sorcerers and magic fucking around.
The man who coined the term Sword & Sorcery and along with Howard was probably the father of the genre.
If you haven't read him you should. Big superstitious Barbarian and his Thief/former mage apprentice 'civilized' skeptical companion go out on kickass "earn coin & whores" adventures.
>Robert E Howard
Dying Earth, Lyonesse, Planet of Adventure, Demon Princes. READ HIM. EN-FUCKING-JOY.
Sword of Welleran, Gods of Pegana all great stories.
Gormenghast. Unfinished but fucking awesome political intrigues etc.
Humorous satire on everything. (early books are meh)
Chronicles of Amber. Children of a Fey king fuck around with each other trying to gain the rights to the throne now that ol' pa is gone.