For me its riding in a car. Not that i'm scared to ride in a car, but when I was a kid I NEVER thought about it. Now, depending on the driver, I don't really want to ride in the car...
Hear me out, imagine having a kid with all the bad stuff that you and I don't want happening. We live here and now and I personally don't find it all too great; kids, though, they don't have a say in that. Huge weight on my conscience.