Heavy Slug Thrower

"This devastating squad support weapon is capable of completely halting enemy advances with a hail of microrockets. It performs so well that it has undergone very little enhancement or modification since its introduction. The Cabal's Colossus heavy infantry units wield Heavy Slug Throwers to devastating effect.

In Guardian parlance, these weapons deal Solar damage."

References

http://db.destinytracker.com/grimoire/enemies/cabal-arsenal