Required Object Types
The required object types page allows you to determine which object types must be implemented on a map in order for a game variant to be compatible.
If any object type in this list has its checkbox checked, then Halo: Reach will not allow players to play this game variant on any base map that does not define that object. For example, if the "Covenant Bomb" object is checked, then players will not be able to play the game variant on any map other than Breakpoint, which is the only one to define the Covenant Bomb.
The list includes several object type names that aren't actually implemented in Halo: Reach, such as the Chopper, Brute Shot, and other Halo 3 leftovers. No, there's no way to magically spawn these in the game.