One that struck me recently, when my kids happened to encounter one -- landline phones. I've had a cellphone-only household since before they were born.
When I was growing up every swimming pool had the small diving board. They were dangerous as hell, but we didn't know or care.
Phone books and yellow pages - Whenever someone drops one off these on my doorstep, I throw it directly into the recycle bin. What a waste of paper.
These are only useful for people who get arrested. I was awoken morning by a phone call from some guy who said he knew juicy. Found us in the phone book and since all his friends/families had cell phones he couldn't get a hold of them from jail. That was fun.
I'd even go beyond this. My kids are 2 and 3, and I can already see DVR\Tivo technology becoming obsolete in the not too distant future. They won't have to queue up a show to record, they'll have on demand access to all of their shows\movies. We don't have cable now, and I have no intention of ever doing so again. My kids will grow up in a world where everyone cuts the cord and gets their programming ala carte. That means that they won't ever get exposed to the crap channels that cable companies make you buy. They'll never see a shopping network channel, and they might never see an infomercial.
Advertising brings in money. The more those avenues expand to bring content to more people, the more opportunities there will be for vendors to sell advertising space.
They'll definitely see commercials, but the days of network programming getting shut down at 2AM and being too tired\lazy to do anything but watch Billy Mays or one of his clones pitch a product for 30 minutes is a thing of the past.
I borrowed an old PU truck from a buddy this week to move some landscaping materials. My kids were fascinated with the hand crank windows and the standard transmission.
I wonder if they'll ever see play ground equipment made of rotting, splintery wood and razor-sharp heat-conducting metal.