Let me be clear, I consider my game design FAR from the level of published game designers.
I got this Game Designer badge for:
"Contributor to The Breached Fortress of Anoros"
but almost any GM who makes up their own adventure would qualify by the same measure. Also, I consider RPG content different from an RPG system.
Having said that, I am an amateur game designer with far too many unplaytested designs at various stages. Some that made it a ways: