In extreme shock models, only the impact of the current, possibly fatal shock
is usually taken into account, whereas in cumulative shock models, the impact
of the preceding shocks is accumulated as well. A shock model which combines
these two types is called a `combined shock model'. In this paper we study new
classes of extreme shock models and, based on the obtained results and model
interpretations, we extend these results to several specific combined shock
models. For systems subject to nonhomogeneous Poisson processes of shocks, we
derive the corresponding survival probabilities and discuss some meaningful
interpretations and examples.