One of mine is reading one of the more expository sections of 1984
in the school library in 11th grade. I think I skipped a period to be there, but I walked out of the library a different person, which I still am. That was maybe the defining moment in shaping my view of history, loyalty, passion, hatred, reality.... everything. If I have "grown up" yet, that was when it happened.
Another was this time, and this one's kind of bizarre, I went through a photo album of my family's life from when I was conceived to when I was nearly three. Something changed. The happiness and innocence in it got to me. I was maybe 10 or 11 when this happened. Up until that time I think I was considerably more.... evil? than I am now. I often desired for the bad guys to kill the protagonists in whatever action shows or Bond movies I watched. If I was watching little kid's shows, I would imagine them being derailed by violence, making the characters cry, stuff like this scene.
I don't know why. The album triggered me to become the exact opposite of that. I am one of the good guys now. I cannot even imagine being the other way. It's so weird.
There are a few others. Those are probably the biggest ones in shaping my personality and feelings.
Edit: Oh, and Mattimeo's story is awesome.