|Laughing man without a doubt.
Spoiler (highlight to view)
He's a better hacker than even the Major. Hell, he hacked the major's cyberbrain numerous times. Not to mention the fact that Aramaki himself tried to recruit him into section 9.
Kuze is in second, since I liked his history with the Major.
The puppeteer (from solid state society) is close behind since his goal was an admirable one, as well as the whole mystery of who he truly is.
"When we remember we are all mad, the mysteries disappear and life stands explained."
- Samuel Clemens/Mark Twain