Probably not 9/11, since I was already in college at the time. But it was definitely a shocking moment. I stepped outside and saw everyone looking down the street. I looked down, but didn't notice anything. Then I looked up and thought "WTF!?!?!" I used to work at a law firm at WTC 1, a few floors below where the planes hit. I couldn't go home because transportation was locked down, so I just went to my next class. After class, I went back to see if they managed to put the massive fire out, but the buildings were completely gone. The whole day was surreal.
Jumping several years earlier, I was on my way home from high school when two black kids asked me for the time. I didn't have a watch, so I said I didn't know. They then said, "Give me your money or we'll hit you." I didn't have money on me, but they kept demanding it. After I pulled out my pockets to show I had nothing, they asked "What school do you go to?" I went to the top high school in the city, which would have been a guaranteed black eye, so I lied and said I'm from another high school. Luckily, they accepted this school and let me go. This happened on my birthday.
Jumping back to grade school, my sister and I ran up the stairs to our apartment to find the door open. Our apartment was robbed and the place was in shambles. The thief took the VCR, cameras, all our video games and cut our piggy bank open. I was paranoid that night, thinking the thief may have poisoned our food. We would end up being robbed again a year or two later.