The creature of the day is the Axolotl, a Mexican salamander. The Axolotl is native solely to lakes Chalco and Xochimilco in Mexico. As Chalco has been completely drained, and Xochimilco has been reduced to a series of canals, the Axolotl is running out of natural territory. As a result, they are currently classified as being critically endangered.
This is bad, not only because of the general 'extinction is bad' arguments, but because of the Axolotl's unique traits as well. Among these traits is a strong case of neoteny, where they can reach sexual maturity without undergoing the metamorphosis into an adult. As a result, they generally stay in their larval forms (above) their entire lives. Metamorphosis can be triggered, either through hormone injections, or through environmental conditions. (adult form below)
While that's interesting, it isn't what makes the Axolotl's status a true tragedy. What's really amazing about the Axolotl is its healing abilities. Rather than scarring around a wound, the cells revert back to a stem state, giving them incredible regenerative abilities. Regeneration of whole limbs is fully possible (some have even run into the problem of regenerating two limbs on one stump). In addition to limbs, they can also regenerate internal organs, up to and including non-vital portions of the brain. They also can take transplants from other Axolotls, with no rejection or loss of function.
Information and pictures from Wikipedia and the Encyclopedia of Life