Demonomicon — Goetia — So Many Satans — Princes & Kings
The Golden Book of Demons — Barkonomicon — The Rainbow Codex
Demons After Dark — Editor's Picks

Editor’s Pick

Some of the spirits in this list didn’t quite fit into one of the other categories, but were too good (so to speak) to be excluded. Others were just amusing. But this is intended to be a writer’s guide to demons, and most of the spirits here suggest a plot, or at least a few plot complications. 

Abyzou

Abyzou

A child-stealing demoness once hanged by her hair by Solomon himself
Bune

Bune

A goetic dragon with a strange relationship with the dead
Cerberus/Naberius

Cerberus/Naberius

The 3-headed guardian at the gates of Hell
Dagon

Dagon

Canaanite god of grain, fertility, vegetation, storms...but probably not fish
Mukīl rēš lemutti

Mukīl rēš lemutti

An ancient example of "demon on the left shoulder, angel on the right"
Nominon

Nominon

A mysterious demon whose name means...name
Nybbas

Nybbas

Hell's mimic, the master of dreams and visions
Penemue

Penemue

The Promethean angel that gave humanity writing (and thus, doomed them)
Samael

Samael

Sometimes demon prince, sometimes Angel of Death, a powerful, complex spirit.
Sigambach and Rabidmader

Sigambach and Rabidmader

A pair of demonic notary publics, keeping a record of sigils and pacts?
Sulac

Sulac

Ancient Mesopotamian spirit that lurks in the bathroom
Tantavalerion

Tantavalerion

For someone at the top of the demonic hierarchy there's not a lot out there about this one...
Vine / Royne

Vine / Royne

Building towers and fulfilling monogamous relationships...also, Hell's official witchfinder.
Zozo

Zozo

A modern demon born from urban legend