Team Megamix, Sonic Retro

Sonic the Hedgehog Megamix (commonly shortened to Sonic Megamix) is a work-in-progress multiperson disassembly modification of the original Sonic the Hedgehog videogame for the Sega Mega Drive / Genesis, developed by Team Megamix and more recently moved to the Sega Mega-CD. The game features the ability to play as one of five different characters: Sonic the Hedgehog, Mighty the Armadillo, Shadow the Hedgehog, Miles "Tails" Prower, and Knuckles the Echidna. It is an extensive reworking of the original game, featuring new art, music, abilities, layouts, and other things.

Overbound Game Studios

Sonic Time Twisted is an open-source Classic Sonic style fan-made game, headed by Overbound. The game tries to improve upon the best features from Sonic the Hedgehog CD and the other Genesis/Mega Drive games. These features including time travel, elemental shields, and 3D special stages. The player controls Sonic and co. and they play like they do in the Genesis titles. Like in Sonic the Hedgehog CD, the player must use time poles (now adjusted to be instant) to travel through two different time zones, Past and Future. In the Past, Sonic must find the Special Stages and collect the Time Stones, while in the Future, Sonic must also find the Special Stages, however, these have the Chaos Emeralds. Beat all 14 Special Stages in each time zone (7 each) and the player will achieve the True Ending. Besides that, the player must traverse through 8 zones, most with 2 acts each, reach the Goal Post at the end, as well as encounter a boss at the end of the stage be it Metal Sonic or one of many loyal Super Badniks.

TriBlox

Halo: Out With a Whimper was a side-scrolling shooter take on Halo's Firefight PvE mode and served as a gameplay demo of sorts for their previously upcoming game Halo: Olympus, cancelled as of 2013.

BlueFrenzy

Sonic Frenzy Adventure is a retro-style fangame developed since 2004, featuring 11 zones and 5 playable characters, including two original ones. The game introduces unique mechanics such as a revised ring system with four levels, various shields with passive effects, and special powers exclusive to Sonic. Players explore each zone, ending in a boss fight, with a storyline focused on defeating EggRobo's mechanical empire. Achievements track high scores and hidden collectibles, and the game offers character-specific routes and challenges.

Nexus Team

Sonic Nexus was a game created by Nexus Team, headed by Slingerland. The game used the Retro Sonic engine by The Taxman who joined the project in 2008. The game began development in the summer of 2006 and had three demo releases, two at the Sonic Amateur Games Expo and one during the summer of 2008. It is a critically acclaimed fangame, garnering comments such as, "absolute perfection of the classic Sonic style" from SAGE visitors and various blogs. The character lineup consisted of Sonic, Tails, and Knuckles.

Stritix

Sonic DL Adventure is a work-in-progress 2D fan-game inspired by Sonic Adventure and Sonic the Hedgehog (2006)

Megaspit

Kirbyhi5

Azurarok Studio

Emerald Team

Emerald Ties is an upcoming Sonic the Hedgehog fan game that features classic gameplay with a modern aesthetic.

BlazeHedgehog

DeltaSpeeds

Headcannon

Streak Thunderstorm

Sonic 101 Games

The Sonic Mapping Team

Dr.Ivo Robotnik (his nick name is Eggman) has invaded the peacefull planet of Mobius! , with his army of robots bent on enslaving all the small animals into being living batterys for his army so that he can turn Mobius into on huge city!.Using a combination of the planets animals , gold power rings , and 7 mythical Chaos Emeralds the Dr hopes to have total control of the planet , thats where you come in...Take control of Sonic The Hedgehog , the fastest animal alive! using the Rings and Emeralds free the animals and stop Dr.Robotnik!

TheBlox

Tri Edge Games

No More Blue