My faves are:
Tsunade - i like her design, her though persona, her abilities, her strenght of spirit and her sad past.
Jiraiya - i like his comedic and goofy persona, his abilities and his devotion towards those who he loves.
Orochimaru - i like his twisted personality, design and abilities.
And i also like these a lot:
Sasori - i like his sad past, his tormented personality, his relationship with his grandmother, his design and his abilities.
Hiruzen - i like his caring personality, his design and his abilities.
Danzo - i like his narcissistic personality, design and abilities.
Onoki - i like his stubborn personality, his design and abilites.
Sakura - i like her personality, design, abilities and i can relate to her desire of "wanting to show others her back".