I think I would enjoy a dinner conversation with:
Sinnathamby Rajaratnam - politician, journalist and one of the co-founders of the People's Action Party (Singapore) against British rule but Rajaratnam seems more interesting than Lee Kuan Yew to talk to over dinner and held a lot of different Ministerial positions during the time Singapore became a success story
Christopher Hitchens - entertaining and I enjoy his wealth of knowledge and perspective on so many different topics
Muhammad Ali - his energy, humour, anecdotes, boxing, his perspective on the Civil Rights movement
Nelson Mandela - resolve in the face of so many set-backs and would get some history lessons
Queen Elizabeth I - would pick her brains about her long reign, strategy and achievements
Marie Curie - discussion of science
Aisha - Prophet Mohammed's wife, political activist, prominent in the 1st Muslim civil war, apparently witty and intelligent - so would find her perspective on events in 7th century Arabia interesting.