To drill a tunnel through solid rock
The Megalaser was a large mining device developed by a scientist named Davis to drill tunnels on Pluto in the 30th Century. Futura vowed to guard the Megalaser until it was safely relocated to Pluto, but moments after making this vow, Prime Evil appeared, intend on stealing the laser and using it for evil. While Futura and Davis were momentarilly distracted by Prime Evil, Sir Trance-a-lot knocked them out from behind with a sleep ray.
Prime Evil took the Megalaser with him to the 1980s and to the center of the Earth. During an earlier visit to CoreWorld, Prime Evil had used a Dark Jewel to extinguish the CoreSun and awakened the Stone Golems from their sleep. The Golems began to capture and enslave the people of the CoreWorld so they would serve as Prime Evil's slave army. Prime Evil planned to used the Megalaser to drill tunnels up to strategic places of the surface world and use his slave army to capture the world's leaders and rule the Earth himself.
The CoreWorldian slaves had trouble positioning the Megalaser exactly right, so that it would bore a tunnel straight to the White House situated in Washington D.C. However, moments after Prime Evil activated the laser, Tracy the Gorilla managed to escape from the capture pike that was holding him, picked up the Golem General as well as his pet spider Collywobble and threw them at the laser, changing it's direction towards that of the CoreSun. The laser re-ignited the sun, which made all the Golem Soldiers turn back into boulders.
The Megalaser was first used in the episode Inside Out.