Itachi Uchiha is invincible. And people try to go against the manga statement are mislead.
The Manga scan:
Now observe the context. "... and combined with sword of totsuka. Hes completely invincible"
Meaning WHEN he has those 2 things out he completely invincible. HOWEVER, the thing is the amount of time he can keep them out ;]. Itachi automatically is not gonna mess himself up by bringing out Susano'o along with Yata and Totsuka.
People don't realize that Itachi's "Prime" that is shown.. comes with also his "Weakest" point.
Hence making his statement, of "Every jutsu (in this case a person) has a weakness".
Yes I agree he is invincible, with the Yata and Totsuka out. But noone is retarded enough to against those 2 things.. obviously they will try to buy time till Itachi's MS starts messing up.