Albus Dumbledore.
According to a recent article in the Guardian, J.K. Rowling said the longtime Hogwarts headmaster is the character from her books that she'd most like to have dinner with. I can certainly understand that. Who wouldn't enjoy a nice feast with Dumbledore accompanied by a glass of oak-matured mead?
Wizards Wireless asked the opposite question in 2007: which character would you be least interested in dining with? My readers were interested in avoiding a companion that might turn them into entrees: Aragog finished in the clear lead.
How about you? Which Harry Potter character would you like to dine with? (Personally, I'd skip all the fictional characters in favor of a meal with the author herself).