iQ for iPhone

From Neutrinos:

Can you narrow down the possibilities to discover the secret in under 20 questions? Challenge a friend to a fun and absorbing game of smarts where you are the secret holder. The game includes three difficulty levels and over 200 secrets including celebrities, animals, and places.

• Play with over 200 secrets separated into three difficulty levels.
• Learn interesting facts about each secret when you're correct.
• Add your own ideas and trivia to expand your library of secrets.
• View the record of play and keep track of who's on top of their game.