Quill Cannon, Launch!

A hedgehog

Some animals protect themselves with painful quills. Porcupines, hedgehogs, and echidnas use quills to fend off predators. A porcupine will rustle its quills to intimidate the enemy. If it doesn't scare the enemy, it will launch its quills as a last resort. And then, YEOWWWW! The predator leaves, whining in pain and trying to remove the quill.

Hedgehogs have somewhat shorter quills. Thus, they defend themselves by rolling into a ball of quill. The quills will pierce the legs of anyone touching it. YOUCH!!
An echidna
Other animals use some kind of quill. Hatpin urchins have sharp quill-like thorns that will be really painful when touched. Seabirds, however, can pluck the thorns or drop the urchin to eat the insides.
Images from Wikipedia