Pickaxe

Pickaxe is a tool used by the Digger Zombie to bypass your defenses. It is made out of metal, so Magnet-shrooms can steal it. When that happens, Digger Zombie comes back out of the ground, and is vulnerable.

Trivia

 * In the DS version, sometimes there is a glitch that, when a Digger Zombie pops up from the back of the lawn and his pickaxe is stolen by a Magnet-shroom, Digger Zombie's sprite will still shows the image with the pickaxe even though the Magnet-shroom stole it. This is easier to see in I, Zombie.
 * This and the Jack-in-the-Box are the only non-armor metallic items of the zombies that can be stolen by a Magnet-shroom.