http://en.akinator.com/
think of someone (real or fictional) and within 20 questions it will guess who it is by asking you yes or no questions.
i played a few times and it correctly guessed:
Jaina Proudmoore (Warcraft)
Arthas Menethil (Warcraft)
Solid Snake (MGS)
Superman
Frodo Baggins (LotR)
Samanoske (Onimusha)
Dracula (Castlevania)
Tidus (FFX)
give it a shot, its good times