We survey some new and old rigidity results for Hessian equations such as special Lagrangian equations, Monge-Ampere equations, and symmetric Hessian equations. In particular, a unified approach to quadratic asymptote of solutions over exterior domains will be presented. Special Lagrangian and Monge-Ampere equations are the potential equations for minimal and maximal "gradient" graphs in Euclid and pseudo-Euclid spaces respectively.