Inspired by this thread.
Much as I’d love to bring Shakespeare here and get his reaction to the idea that his works are classics that are still being produced, my first choice would be Hitler. Mostly to ask him “What the fuck were you thinking?”
I’d like to bring Leonardi da Vinci to the modern world.
Do you get to put the person back in their own time, or are they stuck here?
That’s a good one, but I think Archimedes would be even better. May have been even a little more clever and from a period that we don’t know as much about. We may have more to learn from him.
I’ll be selfish and say my Dad. I miss him.
I’d like to hit up the strip clubs with Ben Franklin.
Jefferson would be interesting.
Mohammed. I want to see him confront the terrorists.
Actually . . . this could end badly.
James Madison, in the hope that he would tell the textualist/originalist judges that they’re nuts, of course the Constitution should be looked at relative to current societal standards.
Of course, he could disappoint me on that one.
Jesus. So that he could read the bible and be all, “WTF?! I never said any of this bullshit! Who’s responsible for all this fuckery?!?”
How funny would it be to hear Jesus swearing.
Winston Churchill. We’d sit around all evening smoking cigars, drinking, watching Marx Brothers movies, and telling war stories.
Genghis khan.
Or you could just read his book, the happy little Mein Kampf. Leave that fucker in hell!
Let’s bring back Don Knotts instead.
I would transport James Madison back. I would be interested to hear what he has say about those 27 words he wrote ( the 2nd Amendment ), as they pertain to our present day.
Well, if we’re including fictional characters, I’m going w/ Gandalf! 
Benjamin Franklin or Mark Twain. I think either one would be fascinating for maybe a day. Then Twain would hit me up for a loan to buy a ticket back to Hartford "I just want to see Olivia again. I am SO horny!"and Franklin would try to get me to invest in some crazy invention, like a death ray. “I tried to get George Washington in on this, but he had some moral scruples about vaporizing Cornwallis’ army, the big pussy.”
Tesla, if only to show him that he was right. Elon Musk would probably like to give him a guided tour of the car plant.
Do I have to know who it is? Can I bring someone who worked on the Voynich Manuscript? Someone from the Roanoke Colony? Someone from Atlantis? Babushka Lady? DB Cooper?
To watch him walk around meeting people and going “My eyes … my chin … my hairline … my ears …”
I’d love to play a game of Warhammer 40K with HG Wells.
(Wells invented table top war gaming in 1913, and W40K’s setting of monstrous alien invaders and a callous and degraded humanity seems like it would appeal to the guy who wrote War of the Worlds and The Time Machine.)