I’m an '80 baby here. I’ve heard the inclusion of kids born in '77-'81 under the Generation X label “justified” by saying that there were two waves of Xers–the Atari Wave and the Nintendo Wave. If you remember the introduction of Atari, you’re an Older Xer, and if you remember the introduction of Nintendo, you’re a young’un, but part of Generation X nonetheless.
'67 baby here. Born smack dab in the middle of the Summer of Love.
But I spent my formative years in the Reagan Era. I remember cable TV was called pay TV, and there were two stations, ON and IT.
I remember my whole family going to visit the family of a friend of mine, because they had just gotten Pong, and it was the coolest thing imaginable.
I do not remember Nixon’s resignation, although I probably should. I do, however, remember coming home from school one day and seeing my mother staring glassy-eyed at the television. She told me “sit down. Watch this. The President Reagan has been shot.” See, she’d already been through Kennedy, and could not believe that she would ever see another assassination, and had always hoped like hell that her children would never experience anything like that.
Challenger? I was 18, and working at a newspaper, of all places. The press stopped. Our boss came out and said “We’ll be down for a while. The space shuttle just blew up.” We laughed and called him a liar. He swore it was true, and told us to take a break, and they’d come get us when the run started again. While we were out, we began hearing reports about what had happened. Most of us were numb for the rest of the day.
Funny, though, I’ve never really identified with GenXers, although technically, I fall in to that category. Kurt Cobain, speaking for me? I don’t think so. 'Scuse me while I go crank up some Asia. 
Now, am I high (possible-- born in early '72, remember Star Wars in the theatre, and may be high right now), or did the “generation X” reference originally signify in sociological terms this group as generation TEN (“X” for you rocket scientists)? As in, since the founding of the country this was the tenth generation, loosely speaking? So post-1970 kids are just Gen XI? Am I making this up, or is there something to my fuzzy memory? Do we need a new GQ question?