Diamondium

Diamondium is a blue and ultra hard mineral created by Professor Hubert J. Farnsworth. It was used to defend the Planet Express headquarters, which can turn into a Diamondium cannon, from Yivo and Philip J. Fry, but failed, as nothing in that universe could stop Yivo. There was a contest of Deathball between Farnsworth and Dr. Ogden Wernstrom to decide whether Diamondium or Diamondillium would be used to protect Earth from the tentacles. Wernstrom was the victor, so Diamondillium was used.

Cables made from Diamondium were later used by Bender and his Army of the Damned to invade Heaven. After the robot succeeded in "rescuing" the inhabitants of Earth, Dr. Wernstrom claimed that Yivo's being allowed to escape was proof of Diamondium's inferiority.

Lately, it has been shown that Diamondium can be found naturally in the universe in the shape of comets. However, the plausibility of this is unknown due to the fact that the only Diamondium comet was found on the first third of the episode Reincarnation, and thus, it's canon is disputable.