Advanced numerical simulations with gas physics are an essential complementary tool with new observations to enable precision cosmology. Using the adaptive mesh refinement hydro/N-body simulation tool Enzo, we are constructing very large synthetic light cones to study upcoming sky surveys from X-ray, Sunyaev-Zeldovich Effect (SZE), and weak lensing observations of galaxy clusters. I will describe some of our initial results of these light cone calculations that mimic SZE surveys with Planck and the South Pole Telescope. In addition, I will discuss simulations that illustrate a new idea for the formation and evolution of rich galaxy clusters that contain cool cores and non-cool cores. We propose a model such that non-cool core clusters (e.g., Coma) have undergone major mergers at an early epoch (z>0.5) which have destroyed the embryonic cool cores. In contrast, we believe that cool core clusters have grown through continuous accretion of smaller mass halos that have not disrupted the central cool cores. I will describe the consequences of this model for using cool core cluster mass estimates as precision cosmology tools.