The Hecatoncheires hurled enormous rocks at the Titans during the Titanomachy.
The Hecatoncheires were three gigantic brothers—Cottus, Briareus, and Gyges—each described as having one hundred arms and fifty heads. Their extraordinary number of hands made them especially suited to overwhelming an enemy with repeated attacks. In Hesiod’s Theogony, they joined Zeus and the Olympians after being released from imprisonment.
Their attack helped turn the war against Cronus and the Titans. The Hundred-Handers took up massive boulders and pelted the Titans with them, while Zeus struck with his thunderbolts. The combined assault broke the Titans’ resistance, allowing Zeus and his allies to seize control of the cosmos.
Lightning bolts are a tempting wrong answer because Zeus’s thunderbolt is the most famous weapon of the Titanomachy. However, it belonged to Zeus and was forged by the Cyclopes. The Hecatoncheires’ distinctive contribution was their use of enormous stones, made especially devastating by their many arms.