I'm with the majority; I would always choose to kill in order to preserve my life or another innocent's life (especially of those I love).
I'd rather live with my decision of killing a potential killer than if there was an innocent person who was killed and I had the potential to stop that action from ocurring. (run-on :\)
I also agree that it is scary to think of the power that I (or even any other person) have to kill. I could choose, throughout the course of the day, to kill just about anyone. If a 'chose' to drive my car into a busy office building, I could very well do that... and end up with deaths.
I'm not a dark person at all, I can just see the potential that any given person has to kill. I'm sure most people have thought of something like this at some point... so don't view me as a morbid, psychotic killer or something.