I've had many people ask me for help with selecting products to sell. Heres the truth, you can pick anything. SO in a world where you can pick anything you should pick something you know at least something about that you can talk about comfortably, because selling something you don't know is really hard, especially as a beginner.
Not sure what you should sell? post a bit about your background, and what your thinking of selling and someone in the community will help you narrow it down or give you more ideas :)