From Halopedia, the Halo wiki
The mec-missiler, also referred to as the mec-missile launcher, is a semi-automatic, homemade, crossbow-like weapon designed by the Ussan Sangheili inhabiting The Refuge. The weapon was particularly used by 'Kinsa and his followers. Mec-missilers fire a spear or a razor-sharp bolt made of metal and wood. Each missiler carries up to four bolts. Mec-missilers are not traditional weapons in Ussan floatfighting, as they are too dangerous.
Mec-missilers were used by 'Kinsa and his followers that were infected with Blood Sickness when they rebelled against Bal'Tol 'Xellus and the loyal Ussans. During the floatfight match between the Ussans and 'Kinsa's followers, 'Kinsa used a mec-missiler. When monitor Enduring Bias interrupted the fight, 'Kinsa attempted to destroy him with a mec-missiler. However, the bolt simply reflected off the monitor and shattered into many pieces, and Enduring Bias proceeded to kill the Sangheili. Later, when the Ussans liberated the sections of the Refuge controlled by 'Kinsa's followers, the insurgents attempted to use mec-missilers to fight back. While Enduring Bias disintegrated the bolts with his laser beam, the rebels were killed by Ussans armed with rocket launchers.
List of appearances