I'm a big fan of Highlander, and somehow the idea of immortals who run around cutting off each others heads seems to fit in the strange World of Darkness. I was thinking about it, and it occurred to me that you might be able to have geists that do this — consume the spirits of other Geists somehow. However, I only flipped through the Geist book a few years back when it first came out. I know that the spirit they bargain will bring them back from the brink. What I'm not sure is if consuming another's spirit would be possible or whether they could halt aging. Would such a thing be possible?
update I should say that Geist is just a thought on my part, a suggested solution, rather than a necessarily desired solution.