Here, on May 16, 2014, I asked for the name of anyone in the USA who is a full-time, specialized activist for reason. I received several suggestions. One was James Randi (b. 1928). Is he a specialized activist for reason?
Unfortunately no one has yet published a biography of James Randi's long, productive career. Trying to decide whether Randi is worth furher investigation as a candidate, I studied three publications, one about and two from Randi. First, the long and informative Wikipedia article  does nothing to substantiate the claim that Randi is a full-time, specialized activist for reason. To the contrary, the article makes clear that, though Randi likes reason, he has been focused on two other goals:
- GOAL 1: Investigating the claims made by a variety of individuals, such as advocates of extrasensory perception, and, where those claims are shown to be false or even fraudulent, overturning ("debunking") the claims.
- GOAL 2: Defending the methods of science, and, as a corollary, refuting pseudo-scientific claims (for example, by supporters of homeopathy). Thus Randi rightly takes both a positive approach to science and a negative approach to pseudo-science (and "flim-flam" in general).
Randi explains and supports science, but he is not a full-time, specialized promoter of reason. Science is not reason. Science uses reason in particular ways, but is not the same thing as reason.* Nor does Randi, as far as I can tell from the titles in his list of publications, contrast reason with mysticism, thereby explaining both reason and mysticism.
The second publication I examined was an informative and entertaining lecture by James Randi on his own channel, "skeptitube." This video is apparently a recording of a lecture he gave at Caltech in 1992. Here Randi describes himself as a "skeptic." He says nothing about promoting reason. He conducts an imaginary experiment. The conclusions he draws are severely limited, which is appropriate for science. A philosopher, by contrast, can survey the world around him and draw general or even universal conclusions—for example, about the nature of reason. Randi's lecture supports science, not reason. They are not the same.
A third sampling of Randi's long list of works is an article he wrote for an online journal he apparently established. The article is "Science, Pseudoscience: the Differences." Once again, the subject is science, not reason. And once again Randi is an able defender of science, but he has little to say about reason. Minor points in his article raise questions about Randi's philosophy, particularly his epistemology. For example, after placing the words the truth in scare-quotes, thus throwing doubt on the idea, he says that truth is unreachable, "though in spite of Zeno's Paradox, we do eventually and essentially get there. But let's not examine that can of worms." (p. 1 of a five-page printout)
Does Randi think that truth is possible? Or is Randi a philosophical skeptic, a person who believes that knowledge is impossible, at least to some degree? Either way, his dismissal of discussion of a "can of worms" is not the stance of a specialized, full-time activist for reason. Such an activist would welcome every opportunity to strengthen confidence in reason by solving puzzles about it.
Randi also makes clear (p. 1) that he opposes religion because religion is based on faith and rejects "reason, investigation, and logic." Randi does not go further in describing either mysticism or reason. So, here too there is evidence of Randi's personal support of reason but no full-time specialization in activism for reason.
In summary, working only from these three samples and from his newsletters which I read decades ago, I can say James Randi has had a long, productive, successful career as a defender of science and an exposer of "flim-flam." He is not a specialized, full-time activist for reason. Randi's relationship to reason is analogous to the imprint a seal makes in wax. The imprint in the wax is a result of the seal. Likewise, Randi's work in supporting science is a result of his respect for reason, but respect for a subject is not the same as specializing in promoting it.
Author of The Power and the Glory: The Key Ideas and Crusading Lives of Eight Debaters of Reason vs. Faith, described here: http://www.reasonversusmysticism.com/
* For the meaning of reason, see my post on August 25, 2009: http://reasonversusmysticism.blogspot.com/2009/08/what-is-reason.html.
 "James Randi," May 18, 2014, http://en.wikipedia.org/wiki/James_Randi.
 James Randi, lecture on proving the negative, http://skeptitube.com/james-randi.php, 1992. I am not certain of the location and time of this lecture.
 James Randi, "Science[,] Pseudoscience: the Differences," http://www.mukto-mona.com/new_site/mukto-mona/Articles/randi/science_pseudoscience.htm, no date of publication.