Call of Duty: Infinite Warfare
The Cleaver appears in the zombies map Attack of the Radioactive Thing. It is an one-hit-kill melee weapon until round 8. The Cleaver can be found inside the Sonova Beachside Market stuck in a dead shark. The player must simply interact with it in order to acquire it. The Cleaver is required for completing the map's main easter egg, gaining access to the Pack-a-Punch and acquiring the Alien Fuses.
Call of Duty: Modern Warfare Remastered
The Cleaver was added as a standalone melee weapon in Modern Warfare Remastered, on the June 27th, 2017 update.