Rereading some of the old development blog posts, and noticed somebody mentioning a World of Darkness hack, which got me to thinking. Here's a few ideas, I don't know if I'll run with them at all, so feel free to contribute your own, or take these ideas and run with them yourself.
VAMPIRES
When you rise at sunset, roll +blood. On a 10+, you're fine for the night. On a 7-9, you feel the pangs: take -1 ongoing until you feed on blood. On a miss, anything you do until you feed is acting under fire, where the fire is losing control.
When you feed on someone, gain +blood equal to how much harm you deal to them, to a maximum of +3.
Playbooks:
The Predator
The Shadow
The Rose
The Prince
The Elder
The Wretch
CHANGELINGS
When you feed upon a mortal's dreams... (stuff)
When you swear a binding oath... (stuff)