Are u talking about a toon of just a girl? I thought u were talking about a toon but everyone else has been posting characters so I'm confused. But I'll go with Rin from Mnemosyne and I'll also go with that toon to answer either question.
for girl butt-kicking anime, I'd go with Black Lagoon of Kara no Kyoukai. For magic girl anime, I'd go with Puella Magi Madoka Magika of Tokyo Mew Mew. But I think my all around favoriete is Black Rock Shooter :)