The following categories exist on the wiki, and may or may not be unused. Also see wanted categories.
- Foxes (1 member)
- Future (1 member)
- G.U.N. (5 members)
- Gallery templates (1 member)
- Game Boy Advance games (1 member)
- Game characters (4 members)
- Game navboxes (74 members)
- Game templates (2 members)
- Game writers (2 members)
- Games developed by Aspect (1 member)
- Games developed by Dimps (4 members)
- Games developed by Hardlight (3 members)
- Games developed by Headcannon (3 members)
- Games developed by Sega Studio USA (5 members)
- Games developed by Sonic Team (21 members)
- Games developed by Sumo Digital (3 members)
- Games developed by the Sega Technical Institute (1 member)
- Games written by Ian Flynn (5 members)
- Games written by Ken Pontac and Warren Graff (5 members)
- Games written by Shiro Maekawa (4 members)
- Gerald's creations (2 members)
- Groups (3 members)
- HTML typing-aid templates (1 member)
- Handheld platforms (9 members)
- Hatnote modules (3 members)
- Hatnote templates (10 members)
- Hawks (1 member)
- Hedgehogs (4 members)
- Heroes (16 members)
- Humans (6 members)
- Hybrids (1 member)
- IDW Publishing (1 member)
- IDW Publishing characters (6 members)
- IDW Publishing groups (2 members)
- IDW Publishing locations (1 member)
- IDW Publishing moves (2 members)
- IDW Publishing staff (2 members)
- IDW Publishing transformations (1 member)
- IDW Publishing vehicles (1 member)
- If-then-else templates (1 member)
- Image wiki templates (1 member)
- Image with comment templates (3 members)
- Immortals (1 member)
- Industrial theme (2 members)
- Infoboxes (16 members)
- Inline hatnote templates (1 member)
- Inline templates (1 member)
- Internal category-link templates (3 members)
- Internal template-link templates (4 members)
- Inventors (5 members)