Sonic Jr. (lost build of unreleased Sega Pico game; existence unconfirmed; 1994) - The Lost Media Wiki

Sonic the Hedgehog 2006 (lost build of Tokyo Toy Show tech demo of

SegaSonic the Hedgehog (lost build of cancelled 32X port of arcade

Shadow the Hedgehog (lost early build of platformer; 2005) - The

Super Sonic (lost build of cancelled Sega CD port of Sega Genesis

Sonic Adventure New Year's DLC (found Sonic the Hedgehog holiday

Editing Sonic Triple Trouble (lost Master System conversion of

Super Sonic (lost build of cancelled Sega CD port of Sega Genesis

Sonic Boom (non-existent lost episode of animated TV series; 2014

Sega Pico Game: Sonic the Hedgehog's Gameworld (1994) Japanese

Sonic Riders (lost build of cancelled Game Boy Advance port of

Sonic the Hedgehog (lost build of cancelled Amiga port of Sega