

Sonic Color Contrast is a modification of Sonic 1 in which South Island is drained of it's color and must be restored through color monitor each zone has a Hub world where all 3 acts are accessed. To get to the next zone Sonic must restore all color to the Hub and All 3 Acts of a Zone, then the next zone will become accessible. There are new power-ups added such as a Sheild that increases jump height, and a reset power-up which resets the level. This lets the player search for color monitors they may have missed, sonic has no new moves, same as Sonic 1, this means no Spindash. The game features an intro cutscene aswell.
Sonic has been on some strange adventures, but none more strange than this one as one day Sonic returns to south island hoping to take a break from Dr. Eggman's shenanigans. Unfortunately today isn't his lucky day as Dr. Eggman has built a color extraction machine and using it drains all the color from south island even Sonic's blue quills aren't safe! However to avoid overloading the machine, Dr. Eggman has offloaded some of the color energy to monitors, once sonic catches wind of this, he sets out to restore color to all the Zones of South Island by busting them open or collecting the 7 emeralds.

The citizens of Mobius just can't seem to catch a break. Dr. Robotnik (AKA Eggman) is yet again up to his no good tricks. Factories and pollution are spreading like wildfire as he's once again trying to take over the world. Fortunately, the Sonic Heroes are never at rest, and once again wage their battle to defeat Eggman's evil forces. However, the heroes have landed in double jeopardy. Eggman's madman descendant, Eggman Nega, has escaped from the Ifrit's dimension, and is wreaking his usual havoc in an effort to destroy the world. He's even captured Eggman's top three lieutenants, the ruthless Team Metallix, and reprogrammed them to do his even more evil bidding. Unlike previous instances of Nega's destruction, Eggman is not fazed. He figures that once he's in control of the world, he can take care of Eggman Nega as he pleases. Unfortunately for Eggman, Sonic the Hedgehog isn't having that. Before he can decide who to dispatch where, he receives a call through the communicator Tails gave him. The message: someone's already on the case. Not just someone, but someones! Apparently, Sonic's very own sister, Sonia the Hedgehog has already caught wind of Nega's evil and is out to stop him. Sonic is a bit eased, knowing full well of his sister's strength and agility. She also lets him know that she has found and teamed up with a mysterious young hedgehog who can move things with his mind. Sonic instantly recognizes that Sonia is with his newest ally: Silver the Hedgehog. Silver has once again traveled through time to ensure that the future is free of Nega's tampering (though he really ought to just stay here in the present, you know). Knowing that the two hedgehogs are more than capable of handling the situation, Sonic leaves it to them, and resumes dealing with Eggman. Eggman Nega is well aware that Sonic is busy with his dimwitted ancestor. However, he'd do best not to overlook a certain factor. The S Factor, Sonia and Silver! It's up to you to lead the unlikely tag team of the physically powerful Sonia, and the psychokinetic Silver on their quest to right the wrongs of the evil Eggman Nega!

Platform / Action / Science fiction
Metal Sonic Hyperdrive is a modification of Sonic the Hedgehog that stars Metal Sonic as the main character role - more specifically a reprogrammed Metal Sonic. The hack also features other characters besides Metal such as: Sonic,Lone Devil (KAZ),Kirby, and even Somari! Each coming with their own unique abilities: Metal can use the Super Peel-Out, and Maximum Hyperdrive Attacks, Sonic can Spindash in traditional fashion. Somari can spindash, but in a less traditional fasion, Lone Devil can use his Sythe to attack and freefall, and Kirby can inhale enemies, no copy abilities.

Sally Acorn in Sonic the Hedgehog 2 (aka Sally in Sonic 2) is a fan-made ROM of the game Sonic the Hedgehog 2 for the Sega Mega Drive, with Princess Sally Acorn as a playable character in place of Sonic the Hedgehog.

Mega Man X in Sonic The Hedgehog 2 is a ROMhack/mod of Sonic The Hedgehog 2 which lets the player control Mega Man X instead of Sonic, with all of his signature attacks, like the charge beam, the wall jump and the dash, and X can also get the weapons from his enemies, like in his own games.

Knuckles' Emerald Hunt is a modification of Sonic the Hedgehog 2 that split off from another hack Sonic 2 Adventure Edition. It's main goal is to mimic the Emerald Hunting Gameplay from Sonic Adventure 2/Battle. Playable characters being Knuckles and Tikal, through each stage you must find and collect 3 Emeralds or Emerald pieces. The Game features the radar from SA2, and a secret Sandwich mode in which all the emeralds are replaced with Sub sandwiches and the Master emerald is replaced with a Subway footlong. It also features the Scrapped Hidden Palace Zone and some Sonic 1 Zones

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.

Platform / Puzzle / Sport / Action
Did you enjoy SNOLF: The Sonic Golf Experience? Did you wish you could experience the magic and the mystery of an entirely golf-controlled hedgehog all over again, but this time in Sonic 3 & Knuckles, and perhaps enjoy more characters? Well, feast your eyes on SNOLF 3 & KNOLF: The Sonic Golf Experience, Part II! This romhack, like its predecessor "SNOLF: The Sonic Golf Experience", replaces Sonic's ability to move with a golf-game mechanic, similar to the kind of thing found in games like Kirby's Dream Course. Sonic remains rolled up into a ball under most conditions, and can only be launched when he has come to a stop. The Rings counter instead counts how many shots you have taken, allowing players to compete to get the lowest score!

Crazy the Hedgehog is a modification of Sonic the Hedgehog for the Sega Genisis, in which you play as an alternate dimension version of Sonic named Crazy. Crazy has to defeat the parallel of Dr. Robotnik, Dr. Mechanik and his robot army as he's attacking North Island, to find the Dimensional Gems! But this dimension isn't exactly like it's parallel, it's similar but different, its a crazy world! This hack features new level palettes and layouts.