Two more nominations - maybe UK-centric though

[McMarco]

Bill Bailey and Billy Connolly.
Comedians, fun as heck, with a great dude look (including, in Connolly's case, a pink or pea-green beard) and a "Yeah, whatever" lifestyle...

[Dude1967]

Billy Connolly most definitely 

[digbys kid]

Billy Connelly, I agree.  I would love to hear him say "I'm the Dude." in his thick Scots brogue..."AyEEEmm da DEEooodah!"

[Dood]

Known to all that know him as The Big Yin. A high-order dude name if ever. Good musician and great attitude to life especially after his upbringing.