Richard Feynman is by far my most admired scientist. He was a physicist that not only contributed greatly to his field but he was so irreverent about it too. He was a talented lockpicker and an inveterate prankster who never allowed being a dignified adult to make him boring.
More than that, he was a brilliant teacher, truly able to break down deep and complex concepts for others to understand.
More than that however is that he was a true skeptic, a critical thinker who never allowed what he wanted to be true to get in the way of learning the real truth.