Airplanes and cats
There's more here, including descriptions of ways to militarize other animals.
The most creative way to use a cat as a weapon happened in World War II. The United States’ OSS (Office of Strategic Services, the precursor of the CIA) needed a way to guide bombs to sink German ships. Somebody hit upon the inspiration that since cats have such a strong disdain of getting wet and always land on their feet that if you attached a cat to a bomb and drop it in the vicinity of a ship, the cat’s instinct to avoid the water would force it to guide the bomb to the enemy’s deck. It is unclear how the cat was supposed to actually guide a bomb attached to it as it fell from the sky but the plan never got past the testing stages since the cats had a bad habit of becoming unconscious mid-drop.
Don't try this at home.