Hardhat Beetle

The Hardhat Beetle is a relative of the Octorok, and is sometimes also referred to as an Octogon. This enemy does not really attack in most games, instead, it acts as an obstacle.

In Link's Awakening, these could only be knocked into pits for them to be vanquished.

In A Link to the Past, there were two varieties: The blue octogons took three hits to kill with Link's Uncle's sword. The red variety took many hits before falling by the same sword.

There is a minigame in Oracle of Ages that requires you to defeat a few of them in a few seconds.

The blue kind also appeared in Four Swords Adventures, where Link could either knock them into pits to kill them, stun them with the Boomerang and slash them several times, or use the Roc's Feather to jump over them and come down on them with his sword.