If you're Mr. or Ms. Pro Crastinat0r, here's a a few more ideas you can pull together quickly.
True Blood character
I don't watch this show but apparently it's about vampires who look like real people; how hard can that be to put together? Makes me look at people on the street a little different though, because I guess you never know who's a blood sucker!
Since a bunch of people seem to be going out as Vampires or Sarah Palin this year, this could make you the ANTI "life of the party"
Paint or sew or draw "vampire slayer" on an old shirt. Get some garlic, a cross or a wooden stake and something that looks like it's holy water.
Or you could dress like a normal person too, now that I think about it Buffy was "one of us." You could also dress up as a priest but it might be hard to find a little boy to walk around with you all night.
This is my costume this year. If you've read my previous post on "punny" Halloween costumes, you'll know I'm not a fan of "normal" run-of- the ol' mill dress-up. I picked up a devil's outfit the other night, just so I would have SOMETHING to wear.
And then it hit me...devil's outfit + the addition of a pin or some kind of label that says "Advocate" Violia!
Added bonus, watch the look on the faces of others when they take in your devil outfit, see the name tag that says "advocate" and then slowly put it all together. Priceless! Or at least I am hoping it is.