I thought these pictures of the Armadillo Girdled Lizard were pretty cool:
Cordylus cataphractus (Armadillo girdled lizard)
Cordylus cataphractus (Armadillo girdled lizard)
Another site I looked at said it is a response when the animal is threatened. Maybe it is able to stay into a sort of a ball that way and lets its armor protect it?