Jeff Goldbloom - He might be hard to get on the show, but I recommend listening to his interview on WTF, especially the last 20 minutes or so. Marc offhandedly says something about his astrological sign and Goldbloom responds with "you know that's bs, right?" Which prompts Goldbloom to talk about reading A Demon Haunted World, praising Neil deGrasse Tyson, and saying that Cosmos was the first show he'd show his kid. He also pointed out that he wore a leather jacket as Ian Malcolm because "scientists are cool."
While he's not a "career-skeptic", he said he's trying to be more skeptical and seemed very excited to promote science and skepticism. It'd be great to hear if he has a "conversion story" and how he gets-along in a business so filled of woo.