You can purchase the first two volumes of the "Daisy California" comic book that I am creating with my seven year-old niece. It's her character, based on her, and her ideas. If you like little children and you like superheroes and you like comic books, then this should, in theory, be right up your alley. If you are unsure, you can visit the Daisy California website (consider "liking" her on facebook!) to preview the two available issues.
These issues are guaranteed to go up in value. Not monetary value, but sentimental/artistic/historical value, as in you'll be able to tell your grandchildren that you got in on the ground floor of what is sure to become a major pop culture phenomenon, etc.