Motoko Kusanagi in 2nd gig. It's a longshot but I think with the right loadout she would take Alucard, and she's also a more interesting character imo. I mean, Alucard is pure badass but with very little character exposition, while Motoko feels more like a living, thoughtful, intelligent person.
And on top of all that: She's a woman who kicks ass. Lots of guys kick ass, but when a woman does it, that's just better somehow.
http://www.youtube.com/watch?v=MGj_XZiRYCI
AndyMacK said:
Nodoka Miyazaki (Negima)
Unless we're talking about "best" as in "winner of an ultimate showdown type thing"-best, in which case it would be Kei Kurono (Gantz).
Gantz is the worst anime of all time, you fail at life, die in a fire.