Uh, I'm not exactly sure what you mean here. If you are talking about contest mathematics type problems that are specifically meant to test cleverness, then I would guess there are very few, if any graduate texts with that specific aim.
I think most people would agree that you don't need to be able to solve olympiad-level problems to do college math. On the one hand, being able to solve olympiad problems certainly demonstrates mathematical maturity and good problem-solving skills, which are important. On the other hand, higher mathematics demands greater competency with abstract reasoning.
But really, if you are reading a graduate text, and the problems aren't sufficiently challenging for you, then either you're a genius or you chose a rather poor text. Chances are, there will be problems that require as much thought as one would need for an olympiad problem.