Depends. Mine are 13 and 15, and we started letting them watch certain specific episodes of South Park years ago.
South Park is certainly TV-MA, I think...
I don't remember exactly when we sat the kids down and made them watch the Big Gay Al's Big Gay Boat Ride episode. My husband thinks our son was seven. The point is, we'd seen the episode and we decided it was something the kids needed to see, since there were topics in there that we wanted to discuss with them. We also showed them episodes on child sexual abuse, economics, Christianity, etc...
Of course, not
everything we show them is educational.

When Snakes on a Plane came out on video in 2007, the kids were keen to see it and so were we. So we had ourselves a "Snakes on a Plane" evening, with our 9 and 11yos.
The point is, we watch TV
together.