I think every generation has a couple of moments that really stick.
For me, there are two:
1) The Space Shuttle Challenger disaster in 1986. I was 11. We watched it live in our classrooms. I still remember the CRT TV on that big, tall stand they'd wheel into the rooms. You know, the kind with the strap that held the TV down?
2) 9/11. I was 26 and living in San Francisco. One of my co-workers, Ed Felt, was on United Flight 93. He was one of the brave souls that fought to bring down that plane and save lots of people by sacrificing himself.
My wife and I visited the 9/11 memorial last year. I hadn't done that before. It was nice to see Ed's name. Rest in peace, Ed.