For me, it's AMD's Lisa Su. She has the technical chops to lead one of the foremost chipmakers in the world, she had the business acumen and strategic execution to bring about a resurgent AMD after years of stagnation, and her ethics are (as far as I have been able to see) impeccable. This is all in the American corporate environment, which is toxic enough to make it all even more impressive, and in a very male-dominated field that markets itself primarily to a male-dominated audience. There must be a very, very short list somewhere of "things that Lisa Su isn't good at"; if you told me that she's also an Olympic gold medalist, I'd absolutely believe you first and verify afterwards. Oh, and she also has an insanely good academic track record (from MIT, naturally) and can handle the media with aplomb.
If I was going to point at a woman today and say "See that? Don't let anyone ever tell you that you can't do just as much as she did", I'd be pointing at Lisa Su. She's not (directly) in a scientist role right now, but she's my STEM role model. Who's yours?