look I'm a huge Conan fan, but the organized grit that he brings to the table I feel best fits a urban Biker look. I would love to read/invest my time into his story telling of a biker gang! That's just me!
I voted Conan, but I'd love, love, love to see Fafhrd & the Gray Mouser done in an Urban Fantasy Setting (Joss Whedon, Hellboy, Dresden, etc). Modern reinterpretation/adaptation of the original stories.
Chaykin and Mignola did the old one's too perfectly, so modern or cyberpunk urban fantasy.