Sonic Team Junior

Sonic Robo Blast 2, abbreviated as SRB2, is a fan game for Windows and DOS platforms. It is a 3D platformer developed by a group called Sonic Team Junior, using a modified version of the Doom Legacy source port of Doom, to allow for such things as optional analog control and true room-over-room (something not possible in the standard Doom engine), as well as the standard gameplay elements Sonic games are known for. It has been in the works since 1998 and is currently nearing completion, though several parts of the game are still missing. Sonic Robo Blast 2 is closely inspired by the original 2D Sonic games for the Genesis and attempts to recreate a game with this style in 3D, though it also borrows elements from the current Sonic games, such as Sonic's signature Air Spin Attack. Entirely original to SRB2 is its Multiplayer mode, a variation of classic first-person shooter games with Sonic elements. Due to being built with a modified Doom Legacy engine, the game is also very easily customizable. Custom levels, characters and even source code modifications can be created with the help of external editors.

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.

ZykovEddy

Sonic the Hedgehog 3D is a free fan game about a famous SEGA mascot, Sonic, and it is made on Build Engine with additional EDuke 32 port. The game was inspired by two classic Sonic series: Mega Drive/Genesis and Sonic Adventure series.

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.

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.

Hello Fangaming

Bowser somehow got ahold of deadly weapons, and is using them to terrorize the Mushroom Kingdom, spilling blood everywhere. It is up to you to avenge the deaths of so many. Annihilate Bowser and his minions with all kinds of weapons.

Sonic 1: WTF LAME is Joke ROM hack of the original Sonic the Hedgehog for the Sega Genesis. While it largely plays like the original game, it is designed as a technical troll that is impossible to beat normally. The hack introduces special "WTF LAME monitors" which, when broken, trigger a high-quality PCM sample of the Benny Hill theme.

Kirbyhi5

Azurarok Studio

GalaxySoftware

Bluehog Gaming Studio

Sparks, MCKaosu, Gamenerd Advance, LarkSS

Anton Huckleberry

Headcannon

Streak Thunderstorm

Obi Van Helgen

Anton Huckleberry

Nemega

Funstar Entertainment