Does anybody know of any games that feature the 72 demons of the Ars Goetia? I just think those guys are all cool as hell, and I am strongly considering making up a game about them.
I envision a deck of 72 cards. The cards will be divided up into four suites (the cardinal elements) and each one will feature an original illustration depicting one of Solomon's demons, and a box of text detailing the beast's rank, the number of legions it commands, and its powers.
This deck of cards would be used as the game's resolution mechanic.
I'll post more ideas here as they appear to me.

Whenever you set out to perform a task that has a possibility of failure, determine the difficulty of the task on a scale of 1-10 (1 being easiest, 10 being hardest). Draw that many cards from the deck and place them face down into a 'task pile' grid.
Completing the task:
1) Wager a number of points.
2) Reveal a card from the task pile.
3) Compare the number of points you've wagered to the "Legions Commanded" value on the card.

If Wager > LC, you have a success. Remove the card from the task pile and shuffle it back into the deck.
If Wager < LC, you have a failure. The card remains in the task pile, but face up.
Sometimes a demon 'favors' you (as indicated on your character sheet). If so, you get an automatic success when you reveal that demon from a task pile, even if you didn't wager enough points. If you did wager enough points however, the demon grants a boon!

When all cards are removed from the task pile, the task is complete and you are free to claim whatever reward was at stake.
When you run out of points to spend on the task, you may take a severe penalty.

I've done Ars Goetia in the Solar System, actually. Let's see, I have something on it here somewhere...

Ars Goetia (R)
This Ability represents knowledge of the pacts of Solomon, an otherworldly covenant established in antiquity between goetic demons and mortal men. (Or that's how the demons tell it; theurgists know that there are no pacts, only laws set down from on high. A subtle distinction.) A character with this Ability can recognize tools of conjuration, elements of ritual and signs of devilry; he knows the purpose and weakness of each goetic demon, he knows how to contact them or seek them out in the world of mortals when set loose. He may even bind them in place or force them to leave this Earth for their place of imprisonment in the Trithemic Constellation, beyond the Seals of Solomon.

The Goetic demons are a finite subset of all spiritual beings of the netherworlds, ranging from the smallest imp to Lucifer himself; they are important in that unlike most other beings, the goetic covenant of Solomon allows them to be summoned on this Earth, making them actually pertinent for the goetic magician.

It goes on in that vein.

I've statted up some Ars Goetia demons as Eidolons for an Anima Prime game, but not yet had a chance to playtest those stats. I plan on having a bunch more statted up, but I'm gonna mix&match from multiple sources rather than keeping to a single edition of the Ars Goetia or the Clavicula Solomonis. My plan is to use such Eidolons in darker-toned A.P. settings of my own devising (I also have some angels and archangels statted up for Theurgy using summoners).