Large insects from New Zealand, called 'Weta', have evolved certain proteins in their haemolymph which prevent ice crystals forming in their cells. This prevents the cell destruction and means that the Weta can survive being frozen.
I'd say this warrants further investigation. If the gene responsible for producing this protein can be identified and transplanted into other animals in a lab environment, we might be able to replicate the effect in a mammal. After that point, if successful, a human trial might be carried out (legal issues notwithstanding).
It has applications not only for life-extension, but also for long-duration spaceflight.