Originally Posted by batonnoir
Probably the mirror...I think he cloned it out to Naruto toward the end of his fight with Sasuke. If not, maybe he will appear in Naruto's subconscious to help like the 4th did.
Itachi will not appear like the 4th did. Whatever Itachi gave to Naruto will inflict some sort of pain whether it's physical or mental. Nonetheless, It will be something that will most likely almost kill sasuke or suppress his powers.
Itachi said it himself that he hopes Naruto will never have to use his "new gift" http://www.narutocentral.com/manga.p...ruto&c=403&p=7
When Sasuke and Itachi Faught, Itachi knew it would be his last fight and bet on Naruto to save his brother.
Itachis question to saving Sasuke to Naruto
It's "when all other things fail" type of gift.