These are all very well written characters with good history and plot. I would add Tobirama, but we need to know more about his child hood. And how he died.
1. Jiraiya (one of the best anime characters imo)
2. Gaara (from miserable life to turning total psycho & not giving fuk most of the times)
3. Naruto (a main character which is not perfect... rarely see that)
4. Itachi/Nagato (definitely unique )
5. Shikamaru (hahaha he is just like me)
Seeing his father (despite the hype and adoration) kill himself for not following the rules he took it upon himself to follow rules to the letter.Even making fun of/lashing out at those that don't(obito being late all the time) Then when his teammate dies (or at least he thought) because of him debating whether to follow the rules he spends most of his time at the memorial stone. Filled with regret.
As a result he loses track of time and breaks the very rules he used to uphold. Inadvertently adopting his dead teammate's habits phrases and excuses. Not to mention the ptsd he got after the whole thing with rin.
Then there's the parallels between him and sasuke that he picks up. The parallels between his relationship with sasuke vs the third's relationship with oro. (Which can be stretched to minato's relationship with obito)