Nelson Rockefeller: an interesting and largely forgotten figure in American politics and culture. Would be interesting to talk to him. As cited above, his knowledge of art was impressive.
Jacqueline Kennedy: I don't think too many people would pass up a chance to meet her, whatever you think of her.
Marc Chagall: an artist who went from overrated to underrated without too many people noticing.
Luchino Visconti: mixed feelings. Amazing films, a very cultured man, but evidently something of a sex pest. I dare say he'd be too interested in recruiting a young Robert Downey Jr. to speak to me either way.
Gregory Peck: I have never heard anything negative about Gregory Peck.
Lauren Bacall: I have never heard anything positive about Lauren Bacall. Don't care - love her.
Gore Vidal: mixed feelings. An interesting essayist and critic but also a supremely vicious person. Also, the one at the party most likely to attempt to make any outsider feel precisely like that.
Isaac Stern: no knowledge of what he was like, but assuming he brought his violin, I'm good.
Yoko Ono: think she gets a bum rap. Still not overly interested in speaking with her.
Robert Downey Jr.: assuming Visconti has not talked the lad into a compromising position in the guest bedroom, yes, I would very much like to meet the young Robert Downey Jr. Lightning in a bottle, he had it.
Lauren Hutton: An intriguing woman, an attractive look. I do hope she stays inflated until she gets home.
Sigourney Weaver: love her and would love to see what she and Bacall made of each other.
I think a young Sandra Bernhard and Halston would fit right in.
My plus one would be either Pauline Kael or John Gielgud.