What do you mean one that IS controversial? Some of the ones you've listed spark so much controversy, or do you mean something so mindblowingly controversial and risky to debate about?
Here some ideas, maybe you're inspired by them
> The Teleological argument
> The Afterlife: Human Construct or Undiscovered Location?
> Human Immortality, Intergalactic Colonisiation and our purpose as a species
> Prostitution and it's place in society
> Freedom of Information, The Internet, The Deep/Dark Web
> Organ Harvesting and alternatives
> The Education System and how imposing should it be on our youth