One of the less known Uchiha Brothers, sometimes Uchiha Tobi is mistaken for Obito. But in the manga, or so I'm told, Tobi reveals himself to Sasuke as Uchiha Madara. (damn, spoiler.. Sorry Naruto manga readers)
Friend: Isn't Uchiha Tobi-kun Uchiha Obito-kun?
Me: No, Tobi reveals himself to Sasuke in the manga.. I'm told..