For all of you guys out there calling Itachi the Soloking, why didn't he just kill Danzo with Totsuka Blade? Seriously, you can't say he had no reason to. Danzo stole Shisui's eye, Itachi was Shisui's best friend. And if Itachi was worried about Danzo touching Sasuke, just kill Danzo.
Because that would have been the most moronic thing to do in the situation. The Uchiha are suspected for the Kyuubi attack and the village is on edge since all of them barring 5 yr old Itachi and infant Sasuke weren't there that night when they were supposed to be. The Uchiha heir killing a respected Konoha elder means instant war. People aren't going to stand for Uchiha attacking influential people in Konoha, someone holding the second most amount of power in the village.
Also, he was 13 then. He didn't possess Totsuka until years after he left Konoha.
Itachi kills Danzo, a war happens, and Sasuke is still in danger since more people out there are out to get him since he's an Uchiha. Not very sound logic. There's no possible way to eliminate all the threats.
Danzo stole Shisui's eye since he didn't trust him and KA is just genjutsu, a temporary solution. What would have happened if a Hyuuga happened to see that the chakra of the Uchiha were disturbed and broke the genjutsu? That plan wouldn't have worked. Both Shisui and Itachi knew that the eye was in safe hands, in the hands of someone who'd use it to defend the village. Why randomly go kill him to get an eye that only works once every ten years, when neither Uchiha have possession of Senju DNA to lessen that lengthy activation time?
You also have to keep in mind that Itachi was somewhat of a pacifist. He only killed when he absolutely had to or to keep up his cover. Nothing more, nothing less. He tends to end fights quickly, for that reason, with genjutsu. It's out of character for him to just get up, kill Danzo out of anger (when Itachi's a calm person and doesn't hold grudges towards anyone, he only blames himself for every bad thing occuring), and let the war happen over that the next day. Glad he didn't do that, lol.