Naruto and Sasuke fusion
I thought about this once, but then said no because it would pure copy of DBZ, even though Naruto manga is inspired in the Dragon Ball manga.
After reading this thread, which got many posts and made it to one of the popular threads this week menu, I thought about another possibility. http://narutobase.net/forums/showthread.php?t=338117
Sasuke has learned almost all jutsus Orochimaru knows, at least the relevant ones and said to him before killing him: I have taken everything from you
I guess you know where I am coming from now... Sasuke taking over Naruto's body.....
But it doesn't mean by force. Naruto manga is really unpredictable, not boring and predictable, and we may see Naruto being defeated, and Sasuke, in order to help him survive, make a reverse way of that Orochimaru's jutsu...
I said this is an unpredictable manga, but there are thigns we can predict, like Naruto being Hokage or getting the Rinnegan! Another way would Sasuke giving Naruto his eyes.