Hatake Kakashi. Must I even say? He has an extremely fascinating personality. Despite his significant losses, he always has a smile on his face. Seeing him like that makes me hurt. He has endured a great deal of loss in his life, yet he still acts unaffected.
Shikamaru is such an interesting character too. I wish they gave him more screen time to show his intellect in battles. It would have made for some really good battle sequences