Master Console

Mainframe computer systems have a special terminal where the system operator can issue privileged commands to the system, to do things mere mortals can't do, like tell the system you've mounted a tape, or to authorize special privileges. When this is a single, permanent terminal, it's often called the Master Console.

Many video games have a master console as well. In this case, the master console is enabled either by a command-line option or a special key, usually the ` (backtick) key at the upper left of the keyboard. When the master console is enabled, one can change many of the features of the game, including changing internal variables (such as the weight of gravity), enable special God Mode features, give infinite ammo, or virtually anything the programmers choose to put in the master console subsystem.

Note the term "master console" is being used here to keep from confusing with game consoles, the dedicated hardware used to play games. You usually can't get a console on a console, not even if it's a Sega Master System.

Interactive Fiction

 * The Dungeon game for the PDP-11 minicomputer (later modified and released for home microcomputers as the Zork trilogy) had a debugger that could be used to change things, variables and constructs in the game.
 * Colossal Cave Adventure had a "MAGIC MODE" command that allowed the game manager, when the game was running on a shared computer such as a mainframe, to restrict times that the game could be played, set the welcome message, and optionally change the password to access magic mode.

First-Person Shooter

 * Quake might have been the first FPS to use a drop-down command-line console. The game's configuration files were actually shell scripts for the console, run through during startup just like your autoexec.bat or .bashrc.
 * Half Life, originally based on the Quake engine, continued to include a console on the Source engine games (Half-Life 2 onwards) which allows you to enable or disable certain features. Portal adds additional features to change some of the functionality of the portal gun. And as Half-Life before, other games produced on Source carry on the convention.
 * The Unreal series' console added an entry-line pop-up version that did not obscure the screen. Unreal engine games frequently implement chat commands by popping up a command line pre-loaded with a "say" command. In later engines, the drop-down hotkey has migrated to F10.
 * Battlezone 1998 has probably one of the most powerful consoles out there, capable of doing stuff like swapping the skybox. In fact, basic console knowledge is required for mappers since the second game's built-in map editor is not exactly user-friendly.

Role-Playing Game

 * The Elder Scrolls Morrowind and Oblivion.
 * Fallout 3.
 * The Neverwinter Nights series.

Simulation Game

 * The Sims series.
 * Spore as well.