I LOVE SAMURAI JACK, I WAS SO SAD WHEN THEY STOPPED AIRING NEW EPISODES D=D=D= anyway, that sig is pretty epic. The black borders on the top and bottom ruin in, though, get rid of them.
i like the borders. not the stock. too soon. maybe again in 30 years when it has the "jetsons" feel to it also not liking the mask or w.e on it
The black line should be much thicker in my opinion, and possibly put behind Jack. I don't know if this was present in the cartoon, but it is certainly present in some Anime and other action cartoons. When an action scene takes place (the picture here is a prime example) the screen narrows, with black borders above and below. The narrow screen creates the impression that the character is moving quicker, and shifts focus easier. It's a common technique, and i got the impression you were trying to create it. If you weren't, i'd recommend you atleast try.