Originally Posted by
DarthEnder
I'm with Arch. They've already shown that Itachi can give people one-shot uses of his Mangekyou power(granted, the other person he used it on at least had a Sharinan already).
Though I can't imagine it's another Amaterasu, cause you can be pretty sure Itachi wouldn't want Naruto to vaporize Sasuke.
I suspect though what he gave him though is something that will either break Naruto out of Sasuke's Tsukiyomi, or negate Sasuke's ability to supress the Kyuubi. My money is on the former.