A little different answer:

My father is a failed career criminal. Money laundering, drug trafficking - that sort of thing. He and my mom divorced when I was young for obvious reasons but they maintained a friendly relationship their kids. Needless to say, I had a very different childhood.

But some things I never really got to experience as a kid:

• Family vacations
• Christmas or birthdays. The reason was because you could never count on having a good or bad Christmas/birthday so my parents decided the best course of action would be to train me to have NO expectations for either of those days.
• My mother was very adamant that I not bring people over to our house so I spent much of my time at home reading or watching TV.
• After school activities. My mom worked evenings, my dad was never on a stable schedule so he couldn't pick me up from soccer practice or whatever. It was my responsibility to come home and take care of my brother after school.
• Cartoons. This is a weird one, my parents figured I needed to grow up fast so while they didn't forbid me from watching cartoons and movies, they encouraged me to watch things more rooted in the real world. As a result, my childhood TV shows were Politically Incorrect and Dennis Miller Live.

In a way, I'm as informed on "adult" things as any other person is but I have no idea what it means to be a child since I have no memory of playing with toys or having birthday parties growing up. I spent Christmas with an ex-girlfriend's family years ago and it was the first time in my life I got to experience the warm loving family thing I used to watch on TV. For a long time, I thought it was just a TV trope like New York City with only white people. Don't get me wrong, my parents loved me but they had to be pragmatic about a lot of things.