Wood Frog (Rana sylvatica)
This species of frog, while not endangered, may soon be threatened by rising global temperatures. It's blood and physiology allow it to undergo multiple freeze-thaw cycles. When it get's too cold, the frogs simply freeze in place, their heart and lungs stop, and they turn into a literal ice cube. Once it warms up again, their hearts start pumping and they resume hopping around. Freezing during the winter helps the frogs by eliminating their need for food for those long months when none is to be had. With warmer temperatures around the corner, these frogs may find it difficult to survive the barren winter unfrozen.
Read about the mechanism frogs use to survive the freeze-thaw cycle, and how scientists hope it can benefit humans. An older article from National Geographic about frogs and Global Warming in general.