Hybrid Weapons are weapons that are able to switch between their usual firing mode and operate as a completely different class of weapon. They appeared first in Call of Duty: Ghosts then in Call of Duty: Advanced Warfare, and were later added in Call of Duty Online and continued to appear in Call of Duty: Infinite Warfare.
Hybrid weapons in Call of Duty Online
Light Machine Gun
Hybrid weapon in Ghosts
Hybrid weapon in Advanced Warfare
Hybrid weapons in Infinite Warfare