What should we stop children seeing?

I think we can all agree that there are some things that we should not be showing to children, so the question is what to control.

I think we can group it into areas:
Sex/Nudity
Drugs (including alcohol)
Violence/Horror
Swearing

Are we censoring too much or not enough?
Is the balance between these areas correct?
Does culture effect what should be controlled?

As with my other threads, I have an opinion but I will let other people speak before sharing it.