The Mouse Lemur from Madagascar is not bigger than a human hand, making it the smallest primate. A dozen can share a tree hole to sleep in, which they leave during the night to find food. (Planet Earth - BBC)

Bats by BioDivLibrary on Flickr.
Recherches pour servir à l’histoire naturelle des mammifères :.
Paris :G. Masson,1868-1874..
biodiversitylibrary.org/page/39564290

mantis shrimp
from wikipedia:
Called “sea locusts” by ancient Assyrians, “prawn killers” in Australia and now sometimes referred to as “thumb splitters” — because of the animal’s ability to inflict painful gashes if handled incautiously — mantis shrimp sport powerful claws that they use to attack and kill prey by spearing, stunning or dismemberment. Although it happens rarely, some larger species of mantis shrimp are capable of breaking through aquarium glass with a single strike from this weapon.