I have to disagree with the Hunt suggestion. He was a good driver and there are always more people who deserve to win a championship than actual winners, but I don’t think he compares to the other choices. I like Hunt though so I don’t want to trample on a favourite :-)
On the subject of Piquet, that photo links to his Wiki page, which also contains this story:
On July 31, 2007 Piquet, after repeated speeding and parking offenses, was stripped of his civilian driving licence and ordered by the Brazilian courts to attend a week of lessons in order to “learn good and safe driving conduct”, and to then pass an exam. His wife Viviane received the same sentence. “I think we have to pay for our mistakes,” Piquet told Brazilian media. “It’s not just a speeding problem, I got tickets for all kinds of reasons, like parking where I shouldn’t.
His son didn’t get a ticket for parking in the wrong place!
I would have to agree that Mansell was probably the most determined and spectacular but i would also have to say Rindt, Andretti and particularly Hawthorn who I also think is highly underrated these days – plus I love the fact he sometimes raced while wearing a bow tie!