The Mezzanine

Yay, Buffy talk! On Dreamwidth!!
Oh, Wes. :D
I think I've seen people argue for a Slytherin Willow, because hacking and magic are also power + ambition for her, not only knowledge for its own sake.
Whatever Spike is, there would have to be some Slytherin or Hufflepuff in the mix because of how loyal he is to his own. I could see it as a Slytherin loyalty -- not to a whole group, but to his select people. And he can be manipulative, and I'd say there's some ambition involved with the whole Slayer of Slayers thing, so a dash of Slytherin seems to make some sense than dash of Puff.