I agree. But for the sake of this poll, I'm throwing out the fact that every individual and type has their own motivations to charge their will power.
I voted ultimately ESTJ. I will explain my reasoning.
When I think of strong will power, I think of a big picture -- something that someone is working towards. Their end goal. Judgers are more big-picture types than Perceivers, so xxxJ.
Now, when it comes to will power, objectivity is going to play a huge role. A Feeler has a preference for empathy and emotions, but a Thinker can push biases like those out of the way. So now we have xxTJ.
Intuitives tend to look at different possibilities. Sensors, however, are more black-and-white types of people, so sensors are less likely to get distracted and more likely to focus on the one thing they're going for. So, xSTJ.
This last (or, first?) letter took me a bit of time to figure out. I would have voted xSTJ if I could. But, since extroverts are more in-tune with other people and the external world, I figured they're more likely to take the initiative to interact with others (or whatever is "out there") to reach their goal. So I voted ESTJ.