Sonic the Hackable2018

Hellfire Saga is a full-fledged Sonic the Hedgehog 3 & Knuckles ROM Hack developed by Red Miso Studios, where Sonic goes through levels that are heavily based on classic 80/90s games and with a dark/spooky theme (Castlevania, Ghouls n' Goblins, etc).

Sonic 2: Pink Edition is a modification of Sonic 2 that replaces Sonic & Tails with Amy and Cream as playable characters, Amy's sprite being based off her modern design. The changes aren't just to the asthetics though, Amy and cream bring their own movesets to the table! Amy bringing her trusty Piko Piko Hammer to swing,jump,whirl and dash through Robotnik's obstacles. Cream bringing the spindash and ability to fly, oh! don't forget about her trusty Chao, Cheese who can attack enemies, even bosses, from a distance!

A hack which combines Sonic 1 levels, Sonic 2 (final and prototype) levels, Sonic 3 levels, and Sonic and Knuckles levels into one game.

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.

Sonic 1: South Island Definitive is a hack by RadiantNexus Team, which seeks to reimagine Sonic 1 by rearranging levels. remixing music, adding features from future games, and readding scrapped ideas in new and interesting ways. Major features: 3 acts of reimagined level design, including one act that has yet to be fully reimagined in any other hack. A miniboss. Massive art overhaul all over the place. Music made by ProjectFM and MechaKnuckles. Menus! A custom splash screen. There's been massive engine overhauls as well, including the Sonic 3 level layout format for massive levels, and the Sonic 3 object manager to go alongside this.

Sonic Sunventure is a ROM hack of the original Sonic the Hedgehog (1991) for the Sega Genesis. It features redesigned levels, new mechanics, custom music, and updated visuals with a time travel theme.

This is a mod which changes Sonic to Gex the Gecko, with gameplay from its first game, including wall climbing.

This ROM hack swaps Sonic and Tails for Mighty and Ray, with adapted abilities inspired by their Sonic Mania versions.