Man cannon
From Halopedia, the Halo wiki
Man Cannon located close to your base or near a spawn point is a term used to describe a technology that is somewhat like the Gravity Lift of the covenant. [1]
The device tosses a player into the air to another part of the map. The user is said to be unprotected during the jump but can attack other players in mid-air, even if they are on the ground.