Well, almost anything you want. While NBA players such as Amar'e Stoudemire wear goggles, the league told Rondo he could not wear sunglasses during the game because opponents must be able to see his eyes.
Here's what he looked like in warmups:
Lisa Salters has more:
But really, all you need to see is the photo below. It's presented without context, because it is much better that way.