Axolotls

(Axolotls are basically amphibian salamanders)

Beyond just looking insanely awesome, axolotls also have extremely strong regenerative abilities.

So strong in fact that they commonly take bites out each other and are still able to survive. What's even more impressive is that their regenerated parts such as limbs work just as good as the originals. They also don't need to worry about growing cancer cells.

(Axolotls that are cannibalistic during their youth will continue to be cannibalistic throughout their entire lives. The way to prevent this is to separate axolotls during that phase)