OK, I'll be uncharacteristically serious for once. My nominee would be:
William F. Buckley, Jr., the late Republican conservative writer, speaker and television host. A man with whom I used to privately correspond in the late 1960s and early 1970s.
His conservatism was the pure New England variety, having more in common with the liberal Thoreau than with any of the current unscrupulous neo-cons.
He also had ethical integrity and humanity, something else sorely lacking in most who call themselves conservatives these days. And a keen, logical mind that sought truth before all else, and wouldn't tolerate the shameless spinning and hypocrisies we see today.
Of course he looked like a perfect nerd, so it wouldn't be on appearances he could have ever converted me. But then someone's appearances aren't what made me realize I was gay, and reject the straight life I once thought I had. And it wouldn't be appearances that could tempt me back.
It makes sense for me to be gay, rather than my senses having enticed me to this life. So that I would only consider reverting straight, if someone as logically compelling as a Buckley, could convince me of objective and common sense reasons to turn away from all the happiness I have ever known in my life.