Death Note is a favorite. If you enjoyed that you should definitely watch Liar Game. It is a live action.

http://www.imdb.com/title/tt0978076/

The first episodes with the Teacher are okay, but it really kicks into high gear when they being playing 'minority rules' later on. Really marvelous!

If you enjoy a real challenge read The Book of the New Sun by Gene Wolfe. It's the most rewarding puzzle I've ever tangled with. I was up for days, weeks, thinking about it afterwards.