What is this? This is the sort of list some edgy Christian would put together. I partly take that back; this list is very Atlas Forum 
In the modern era you could say Jonas Salk for his medical contributions and or Gloria Steinem for her views on feminism and early advocacy of a lot of current mainstream issues. James Randi was the most effective of the 'skeptics.'
I agree with the inclusion of Carl Sagan.
If your list is primarily Brits making a quick buck fifteen years ago to argue on Christian college campuses that's quite sheltered.
Edgy Christians? I mean, those "types" would be offended by all of the above anyways, which makes them the antitheses of these ideologies. Now that you mention him, James Randi did a great job of skewing the fantastical crowd. Sad to learn of his passing last year, hopefully new generations of skeptics will continue his legacy of showing the truthful nature of science to the world. Gloria Steinem does not cross my mind for inclusion because I think of her more primarily as a social reformer who was secular than an outspoken secular figure, though she did win the AHA Humanist Award. For a wonderful humanist in charge we should thank Dr. Anthony Fauci who has protected America against this time of crisis, who lead the charge against anti-intellectualism that is prolonging the pandemic in America. Still, he's a man of science than a philosopher on the illogical nature of religion.
Say what you will about the New Atheists, they were brave individuals who spoke out against religion when it was more fashionable. Nowadays I think you can go around to people and say you're a nonbeliever because of these men great task in challenging the superstitious status quo that had a hand in help from the U.S government during the Bush era.
I really don't think secularization is stochastic enough of a social force to be credited to (or blamed on, depending on your priors) Richard "dogs in full 69" Dawkins or Sam "if I could wave a magic wand and get rid of either rape or religion, I would get rid of religion" Harris, James. If one absolutely insists on great-manning this then a better figure to bring up in this context, in an own-petard sort of way, might be Ralph Reed.
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