Naked mole rat
It must be difficult to maintain a vibrant self-image if you're a bald rodent, but it's not an issue for the naked mole rat. These animals live underground in insect-like colonies, and they have little need for good eyesight. Their hairless bodies are also an adaptation for their underground environment.
Interestingly, naked mole rats are also among the longest living of all rodents given their size (they can live for nearly 30 years), and they have a remarkable resistance to cancer.