My top pick would be Condoleeza Rice. Smart, tough, way more effective as SoS than Clinton ever was.
Short list -
Madeline Albright
Notorious RBG (I don’t agree with her, but I’m pretty sure she can force-choke, and that would be a cool power for the president to have)
Elizabeth Warren? Maybe.
Condoleezza Rice
Elizabeth Dole
Lynne Cheney
Ivanka Trump
And that’s just off the top of my head. I could probably come up with 20 or 30 more if I dug around a bit. Contrary to the notion promoted in liberal circles, most conservatives by far would have no problem voting for a woman provided she held conservative views. Same with black candidates as well. I’m happy that Clinton is now out of the running as it holds open the possibility that the first female president will be a Republican. I’d like the country’s first black president to be Republican as well.