Ooo, hm. Hillary, of course -- she has all the necessary experience. Marcy Kaptur, one of the great pragmatic progressives in the House comes to mind, as does Al Franken, who has built a reputation as a hard worker. Former Iowa Senator Tom Harkin would have made a good president, I think; I was a supporter of his campaign in '92.
I think the last Republican that didn't make me want to hide behind the couch was Jon Huntsman -- so of course he didn't make it much past New Hampshire when he ran in 2012. I'm a combination of disappointed and optimistic that he's going to be Asshole's ambassador to Russia. Huntsman had been Obama's ambassador to China, so he has diplomatic experience. I am bothered that he's signed on to Asshole's administration, but at the same time, if I had to pick a Republican to send to Russia as ambassador who is also least likely to have been engaged in campaign and pre-inauguration illegal meetings, it would be him. I suspect that he accepted the post thinking 'if I don't do it, what kind of psychotic will they send in my place?'
Narrowing it down to just one, though? I can't think of anyone on the scene right now who I think would be considered a great president. I can think of a number of people who would be good presidents. Thinking strategically, my own senator Sherrod Brown would help bring the Midwest back into line - yet another Midwestern pragmatic progressive. He won't have an election back home to worry about, since his re-election campaign will be in '18. So I'll go with that for right now, reserving the possibility of changing my mind.