Real Bombchu

The Real Bombchu is a reappearing enemy in the Legend of Zelda series. It is a volatile creature most resembling a large rat. It uses its explosive tail to harm others and simultaneously destroy itself. It inspired a special type of bomb known as the Bombchu. The Real Bombchu interestingly can run across water to attack Link.

The Legend of Zelda: Majora's Mask
The Real Bombchu cannot be defeated by a sword without Link suffering damage from its self-destruction in turn. However, the Real Bombchu can be destroyed from a distance with projectiles, such as arrows, or by defending against it with a shield; which will effectively flip it over and make it explode. Another strategy is to avoid the Real Bombchu until the explosives on its tail detonate. Also running over them with Epona will kill them without loss of ammo or health.

The Legend of Zelda: The Wind Waker
In The Wind Waker, Link encounters Bombchus in the Forsaken Fortress and in a submarine near Headstone Island. They are not Real Bombchus like the ones in Majora's Mask but rather a variant of rat with different coloration and the ability to throw bombs. The quickest and most reliable way to exterminate these uncommon pests is to target them and hit them with the Boomerang.