How about running away to join a terrorist training camp?
Go for a sex-change operation?
Be arrested for massively seeding illegal music and movies with BitTorrent?
Sex Change.
Damn, that’s taken. Now that I think about it, getting your name changed can be shocking too. “I’m not Junior anymore, Dad. I legally changed my name to ‘Urban Shocker’.” I think that would have made my mom cry when I was 18, after she laughed at me for awhile first.
Wear skinny jeans and neon colors…
Haven’t spent much time in the deep South, have you?
I lived in South Carolina for an unfortunate 5-odd years, and seeing a carload of young white kids hanging out the windows and screaming “NIGGER!!” while passing a black dude walking down the street happened so frequently that it lost all shock value. Even in the refined bastion of gentility of downtown Charleston, hearing racist bullshit coming from young white people was so frequent that it only caused resigned, dismayed headshakes rather than outrage. Even among the black people.
Polyamory is probably the most shocking, even though it was invented a long time ago. I guess maybe precisely because it is so old and got outside our mental picture so long ago. Maybe slavery would have the same effect.
Terrorist training camp would also be a shocker for someone in the US or Japan. In Europe, maybe not so much (not to mention Africa and most of Asia).
Other than that it is all boiling down to subculture A being shocked about kid in subculture B. But after all is being said and done, it is all old hat.
Has there been any real cultural revolution in the last 15-20 years? Something that today’s parents would not only disapprove but actually fail to even begin to understand? Just as being openly gay, interracial love, recreational drug use and rock and roll were in their times?
Everyone has a button somewhere and some kids can be truly excellent at finding buttons. So it doesn’t matter what society does or doesn’t approve of, an individual kid can always find an individual parent’s button.
And if the parent has a group of like-minded friends, their kids, as a group, probably know that there’s an established button-territory that they could go for as a group.
It doesn’t necessarily have to be big and heinous. Openly peeing on the front lawn would set me off.
The one young lady on our street is dressing and living as if it was the late 1950s; she is currently 17 and has done so since about age 10. Poodle skirts and Barbies and all the rest. Her parents, both heavily tattooed and aging punks, can’t figure out where they went wrong but they are supportive of her rebellion.
Tithe.
I was complaining to my 15 year old son about how I had to mow my (big) lawn instead of going out on my weekday off last week. He managed to find a 17 year old friend who gave him a ride to my house. Together, they mowed my lawn (over an acre with a push mower) and used the weedwacker, achieving a very good result. My son bought lunch for his friend, and gave him a few bucks for gas.
He’s a good kid, but is not into manual labor. I was shocked.
When (not if) my nephew comes out of the closet, believe me when I tell you that his dad (my brother) is going to be shocked. Maybe “shocked” isn’t the right word. More like “enraged to the point that he may actually try to kill him.” Mrs. Homie and I are already planning for the day when my nephew has to move in with us.
I think most of the stuff being mentioned in this thread does not count because it is not specific to our times.
The only thing that is very specific to our times is sexting. It was not possible before and adults are shocked by it.
Coming out as a furry might count as a recent development.
They could become extremely straighlaced, judgmental and religious. 
In all seriousness…my first ‘rebellion’ against my parents was sneaking out to get a haircut. They wanted me to grow it long and I liked it real short.
“No son of mine will speak text! As long as you live under my roof, you’ll type out your sentences in full!” “gay” “GO TO YOUR ROOM!”
You see, that is weird enough and new enough that it fits the bill of what I am asking.
As for sexting, it is just the newest flavor of flashing. First it was live, then it was Polaroids, now it is instant messages. The general idea remains very much the same, though.
Yeah, but did 12-year-old girls used to be flashers?
They probably played “Doctor” or “I’ll show you mine, you show me yours,” with other neighborhood kids.
This was one-on-one, though, right?
I don’t think 12-year-old girls “showed theirs” to all the boys in the neighborhood or the entire city, which is what sexting* basically amounts to
*and its related activity, uploading nude photos on the web
True. I guess 12 year olds probably aren’t thinking it through that much, though. If you’re just sending it to another guy your own age, you’re probably not thinking of it terms of everyone can see it–just that one guy.
Tell them they’re in a relationship where they’re going to live as a dom/sub full time.
I’m imagining my parents’ reactions to things in this thread, and I think that would get them the most.