Rebecca, or Revy, one of the most unapologetically badass chicks I've ever seen, from the Black Lagoon manga and TV series.
The pen sketch took me about 20 minutes to draw, and about 3 hours to render in Photoshop. The toughest part was her arm tattoos - the design changes between episodes, and sometimes within a single episode. I took a few screengrabs and did my own version.
Revy & Black Lagoon were created by Rei Hiroe.