I don't remember Elvis dying, would have been 7, but I remember how every town had a funeral procession for him and remember when the one in our little town passed by.
The Beirut bombing stick out in my mind because I was in a military family. I remember hearing about it and then walking to school and telling a friend about all the people who died and he replied "so?"
Challenger: was home skipping school and missed it live, but watched the rest of the coverage.
Columbine: perhaps the most amazing news event I have ever watched live. (I missed most of 9-11 due to stupid meeting that they did not cancel)
Remember learning about TWA 800, Princess Di and a whole bunch of other news events via online chats.
The biggest "Holy shit!" moment for me had to be turning on the TV and learning that they had found Elizabeth Smart alive. That is probably the best happy news story I remember since so many of these events are based on bad news.