I'm still trying to figure how (and why) his name got changed from Jubilex to Juiblex. Was that just a typo that got perpetuated, or what happened there?
I never noticed it was spelled Juiblex and not Jubilex until I was corrected on this board and looked it up. p.17 of the 1e MM has it as Juiblex. Turns out I had been saying it wrong since I first read his entry in the 80's. Are there any older references to him?
I like the idea of Fraz Urb'luu better than the rest, mainly because of the deceit angle, but am utterly fascinated by Sepulchrave's take on Graz'zt as "the adversary" and Demogorgon as the ur-demon.
I'm with Shemeska in that Demogorgon is an old favorite of mine. But... My portrayal of demons is rather heavily influenced by Warhammer. Especially the WH40K fiction from Black Library, I try to make the Abyss like their Chaos Worlds and use their demons as inspiration often stealing the names and habits of various greater demons/demon princes/etc. Use all the 4 Chaos Gods as powerful Demon Princes.