en.akinator.com (http://en.akinator.com)
Basically think of a real/fictional character and it will eventually narrow it down to your character after some questions. Crazy how it gets them.
took it 20 questions to guess David Cameron
I was thinking about David Wallace from The Office.
After 25 questions it gave me Michael Scott.
After 25 questions it was wrong.
After 50 questions it was wrong.
After 80 questions it was wrong.
I was thinking of Paul Twiceborn from The Fionavar Tapestry.
Everything I've done it has done in less than 40 questions.