I really love the Proust Questionnaire. You can find numerous links about what it is and its history, but the basic truth is that it is a parlor game, and Marcel Proust evidently played it. Legend has it that someone wrote down the answers he gave once as a teenager and then again later in life.
I first came across the questionnaire while living in France and watching Bernard Pivot host Bouillon de Culture. At the end of each program, he would ask a handful of the questions to the major scientist, artist, or politician he'd interviewed. I found so many of their answers fascinating. You may have heard James Lipton reference Bernard Pivot and ask the questions on his program, Inside the Actors Studio.
I've played this game with a few people over the years. In my opinion, it's best played one on one or in very small groups so that everyone will feel that they can be more forthright. I remember certain people I've played this with, and even more so, I remember certain answers people gave that really surprised me.
Though questions may differ or more questions may be added, the real beauty of it is that your own answers change over time. Of course you can find lists with hundreds of questions, but these are usually some of the basics:
What is your idea of perfect happiness?
What is your greatest fear?
What is the quality you most admire in a man?
What is the quality you most admire in a woman?
What is your most marked characteristic?
Which historical figure do you most identify with?
What is the trait you most deplore in others?
What is the trait you most deplore in yourself?
What is your greatest extravagance?
What is your greatest regret?
What do you consider the most overrated virtue?
If you could change one thing about yourself, what would it be?
If you could change one thing about your family, what would it be?
Who are your favorite writers?
Where would you like to live?
How would you like to die?
"The thoughts and opinions of one human being, if they are sincere, must always have an interest for some other human beings."
- Mary A. Ward