It's been out since 2007 and I've only stumbled upon it today.
Akinator, the Web Genius
On the menu on the left, click Play.
You're supposed to think of a character either real or fictional and answer the genie's questions so he can guess.
I guessed Cookie Monster and it got it right. Hahaha...
The rationale is the more popular your chosen character is and the more similar the answers you supplied the genie is with its database, the more accurate the genie's answer.