It's definitely between Blade and Hannibal King. One's a badass dhampir vampire hunter, the other's a wisecracking vampiric detective.
I'm also a fan of the version of Abraham Van Helsing from the Dracula movie with Gary Oldman, even though I did not like the movie itself.
Edward from the Guilty Pleasures novels/comic books is pretty badass too. Your Edward sparkles? Mine carries a friggin' flamethrower.
...would Walter from Hellsing count? I mean, c'mon, he's the Angel of freakin' Death. And he's a butler. You can't get more badass than that.
In the shallow holes of a thousand eyes
In the knee-deep graves of future survivors
The fleshless guests live off children of the past
Their aging fingers cast the Shadow of Death