Call of Duty 5: SP Utility Scripts

“Utility scripts” are referred to as the scripts that are commonly used. For example, in the script directory, you will see several scripts with the prefix of an underscore, (i.e. _anim.gsc). These are known as the _utility scripts.

Utility	Info
_anim.gsc	This handles playing the various animations on AI, from body animations to facial animations to interactive animations.
_autosave.gsc	Contains functions for executing game saves and checkpoints.
_callbackglobal	Co-op call back functions.
_callbacksetup.gsc	Contains set up functions for Co-op callbacks.
_drones.gsc	Logic and functions that handle drones (non-AI).
_hud_util.gsc	Contains common tasks functions for player HUD.
_introscreen.gsc	Functions pertaining to introscreens before missions start such as date/time/place.
_load.gsc	Loads up scripts needed for the game/missions to work properly.
_loadout.gsc	Functions to player load outs; weapons players start with and the view model arms.
_spawner.gsc	Gold mine of functions for AI spawners here, most of which can be used by Radiant as KVPs.
_utility.gsc	Contains a lot of common tasks scripters use. Odds are, if you need to script a common functionality that other maps demonstrate, it might be in here.
_vehicle.gsc	This handles playing the various effects and animations on a vehicle. Most things you see in the vehicle menu in Radiant are handled here. There's all sorts of properties that you can set on a trigger to access some of this functionality.
_vehicle_ai_anim.gsc	This is where all the vehicle / AI interactions happen.
_weather.gsc	This is where all the rain/ thunder/ lighting effects happen.
_zombiemode.gsc	High level script for the Nazi Zombie mode.

Sources: Treyarch's Wiki