My all time favorite fictional party is the one at Holly Golightly’s apartment in the movie Breakfast at Tiffany’s (I read the book, indeed, it is the only Capote novel that I have, as yet, read, but the movie made a more startling and powerful impression on me).
My new second favorite might be the one in Cicero’s De Natura Deorum or, On the Nature of the Gods. Intelligent men having deeply thought-out conversations on ideas passionately held. It’s like one of Plato’s dialogues, but not everyone gets railroaded by Socrates, which, let’s be honest, would probably not be that fun to experience. Just ask Gorgias.