Suggested by Shaker RedPandamonium: What is something that you would never do in a gazillion years? And I'm going to add the qualifier that we're talking about positive things people do for pleasurable self-fulfillment, not vile things people do to harm.
(I realize those aren't precisely distinct categories in all things, but you get the drift.)
So what would you never do? Skydiving, bungee jumping, scrap-booking, parenting? Do tell!