There are two - my current boss and one of my brothers-in-law. My brother-in-law has a photographic memory so he remembers everything he reads and sees. You want him on your team when you play Trivia!
I actually thought about this for a few minutes. I know many really smart people. There are two that really stand out for me and they were both professors, one in undergrad and one in law school. My professor for Old Testament Survey in college was so scholarly it took half of the semester for us to even begin to understand what was going on in that class. He assumed we all knew much more than we did. I worked my tail off in that class and made the only A. The other one tied for first place was my Constitutional Law professor in law school. While I did not like her very much as the dean of the school, she was a brilliant Constitutional scholar and I was fortunate to study under her.
I'm not intelligent enough to know who is the most intelligent. I am intelligent to know that I can learn things of value from everyone I personally know.