Naruto Shippuden Episode 34

[Buffalobiian]

Are we mixing up "tool" here with "follower/student/disciple"? I'm taking tool here to mean someone who's being used, without using the other person in return. The latter case is called co-operation. Sakura may indeed belong to her own team, but I would imagine her life in the past 2.5 years to be training and serving Tsunade, much as Shizune might have done earlier in her life. Only now her job is closer to that of an attendant, and given her relationship with Tsunade (you can call it her uncle's fiancee if you ignore the master/disciple one), and we haven't been told of any other family members, it's only natural that she follow her around, and assist/criticize her not unlike how a sibling would.

edit: tool implies that the person is a pawn. Used for a greater purpose, and completely dispensable. The "master" of that tool most likely has no emotional connections to he/her, and feels no shame in using that person to do whatever task the master desires. I don't think this quite fits the Tsunade/Shizune scenario.

Haku could have indeed be considered a classic example of a tool, if it wasn't for the last part where Zabuto cries, though he indeed didn't feel any shame when he was USING him, it was only after his death and some Naruto-talk that he felt guilty/moved.

edit 2: or maybe the three sound ninjas Orochimaru used in the Chuunin exam. I doubt he had any feelings for them really.