The following categories exist on the wiki, and may or may not be unused. Also see wanted categories.
- Marvel vs. Capcom (Series) (4 members)
- Marvelous Entertainment (Publisher) (4 members)
- Marvelous Inc. (Publisher) (1 member)
- Marvelous USA (Publisher) (1 member)
- Mass Effect (Series) (3 members)
- Mass Media Games (Developer) (1 member)
- Mastertronic Group (Publisher) (1 member)
- Mastiff (Publisher) (3 members)
- Matt Hazard (Series) (2 members)
- Maximum Family Games (Publisher) (1 member)
- Maximum Games (Publisher) (1 member)
- Maximum SPURS threads (Config) (5 members)
- Medal of Honor (Series) (4 members)
- Media.Vision (Developer) (1 member)
- Media Factory (Developer) (1 member)
- Media Molecule (Developer) (4 members)
- Mega Man (Series) (2 members)
- Memories Off (Series) (2 members)
- MercurySteam (Developer) (4 members)
- Metal Gear (Series) (6 members)
- Metal Slug (Series) (3 members)
- Metalhead Software (Developer) (1 member)
- Metalhead Software (Publisher) (1 member)
- Metroidvania (Genre) (1 member)
- MicroProse (Developer) (1 member)
- Micro Graphic Image (Developer) (1 member)
- Microphone type: Disabled (Config) (1 member)
- Microsoft Studios (Publisher) (1 member)
- Microïds (Developer) (2 members)
- Middle-Earth (Series) (1 member)
- Midnight City (Publisher) (2 members)
- Midway Austin (Developer) (1 member)
- Midway Games (Developer) (3 members)
- Midway Games (Publisher) (8 members)
- Midway Studios Los Angeles (Developer) (1 member)
- Midway Studios Newcastle (Developer) (1 member)
- Mighty Rocket Studio (Developer) (1 member)
- Milestone (Developer) (16 members)
- Milestone (Publisher) (6 members)
- Millennium Kitchen (Developer) (1 member)
- Minato Soft (Developer) (1 member)
- Minato Soft (Publisher) (1 member)
- Mine Loader Software (Developer) (1 member)
- Minecraft (Series) (1 member)
- Minority Media (Developer) (1 member)
- Minority Media (Publisher) (1 member)
- Missing GameID parameter (GameID) (6 members)
- Missing GameID parameter (Infobox) (0 members)
- Missing IRD parameter (GameID) (0 members)
- Missing game mode parameter (Infobox) (736 members)
- Missing genre parameter (Infobox) (17 members)
- Missing internal resolution parameter (Infobox) (2,034 members)
- Missing release date parameter (Infobox) (108 members)
- Missing release type parameter (Infobox) (36 members)
- Mobile Suit Gundam (Series) (13 members)
- Mojang Studios (Developer) (1 member)
- Mondo Productions (Developer) (1 member)
- MonkeyPaw Games (Publisher) (2 members)
- Monkey Bar Games (Developer) (5 members)
- Monkey Island (Series) (1 member)
- Monolith Productions (Developer) (6 members)
- Monopoly (Series) (1 member)
- Monster Hunter (Series) (2 members)
- Monumental Games (Developer) (2 members)
- Moonbite Games (Developer) (1 member)
- Moonbite Games (Publisher) (1 member)
- Moonbot Studios (Developer) (1 member)
- Mortal Kombat (Series) (4 members)
- Mossmouth (Developer) (1 member)
- Mossmouth (Publisher) (1 member)
- Most Wanted Entertainment (Developer) (2 members)
- MotoGP (Series) (6 members)
- MotorStorm (Series) (4 members)
- Move Street Cricket (Series) (2 members)
- Move handler: Fake (Config) (1 member)
- Move handler: Mouse (Config) (3 members)
- Moving Player (Publisher) (2 members)
- Mugen Souls (Series) (2 members)
- Multi-platform (Release type) (1,165 members)
- Multiplayer (Game mode) (814 members)
- Multithreaded RSX: Off (Config) (2 members)
- Multithreaded RSX: On (Config) (24 members)
- Music (Genre) (83 members)
- Mutated Software (Developer) (1 member)
- Mutated Software (Publisher) (1 member)
- Muv-Luv (Series) (5 members)
- Mycom (Publisher) (1 member)
- Mynavi (Developer) (3 members)
- Mynavi (Publisher) (2 members)
- N-Space (Developer) (1 member)
- NASCAR (Series) (6 members)
- NBA (Series) (3 members)
- NBA 2K (Series) (13 members)
- NBA Live (Series) (4 members)
- NCAA Basketball (Series) (3 members)
- NCAA Football (Series) (7 members)
- NHL (Series) (10 members)
- NHL 2K (Series) (4 members)
- NIS America (Publisher) (2 members)
- NOW Production (Developer) (3 members)