Undying by Paul Riddle is a diceless RPG about vampires preying on humans and fighting each other for dominance.
I've been interested in it for a couple of years now. It's currently being kickstarted and the rules are available for free over there: Undying kickstarter
I'm going to read through it over the next couple of days, posting my notes in the comments. I think this is something it'd be fun to run, soon.