Sonic the Hedgehog

Sonic the Hedgehog is a character from the Sonic the Hedgehog series. He appears as the main protagonist in (nearly) every different canon in the series.

Het

 * Sonamy is the ship between Sonic the Hedgehog and Amy Rose.
 * Sonally is the ship between Sonic the Hedgehog and Sally Acorn.
 * Soniona is the ship between Sonic the Hedgehog and Fiona Fox.
 * Sonouge is the ship between Sonic the Hedgehog and Rouge the Bat.
 * Sonaze is the ship between Sonic the Hedgehog and Blaze the Cat.
 * Sonilac is the crossover ship between Sonic the Hedgehog and Sash Lilac.
 * Sonerci is the ship between Sonic the Hedgehog and Perci.
 * Soneezie is the ship between Sonic the Hedgehog and Breezie the Hedgehog.
 * Sonicole is the ship between Sonic the Hedgehog and Nicole the Holo-Lynx.
 * Soneena is the ship between Sonic the Hedgehog and Zeena.
 * Sonbunnie is the ship between Sonic the Hedgehog and Bunnie Rabbot.
 * Soneam is the ship between Sonic the Hedgehog and Cream the Rabbit.
 * Sonelise is the ship between Sonic the Hedgehog and Princess Elise.
 * Sondonna is the ship between Sonic the Hedgehog and Madonna.
 * Soniara is the ship between Sonic the Hedgehog and Tiara Boobowski.
 * Soneach is the crossover ship between Sonic the Hedgehog and Princess Peach.
 * Sonicks is the ship between Sonic the Hedgehog and Sticks the Badger.
 * Sonikal is the ship between Sonic the Hedgehog and Tikal the Echidna.
 * SonMiku is the crossover ship between Sonic the Hedgehog and Hatsune Miku.
 * SonMerna is the ship between Sonic the Hedgehog and Merna the Merhog.
 * Sonalina is the crossover ship between Sonic the Hedgehog and Rosalina.
 * SonMina is the ship between Sonic the Hedgehog and Mina Mongoose.
 * Sontena is the crossover ship between Sonic the Hedgehog and Palutena.
 * SonDash is the crossover ship between Sonic the Hedgehog and Rainbow Dash.
 * Sonmo is the ship between Sonic the Hedgehog and Cosmo.
 * Sonmaria is the ship between Sonic the Hedgehog and Maria Robotnik

Slash

 * Mephonic is the ship between Sonic the Hedgehog and Mephiles the Dark.
 * Sonadow is the ship between Sonic the Hedgehog and Shadow the Hedgehog.
 * Soneggman is the ship between Sonic the Hedgehog and Doctor Eggman.
 * Sonespio is the ship between Sonic the Hedgehog and Espio the Chameleon.
 * Sonilver is the ship between Sonic the Hedgehog and Silver the Hedgehog.
 * Sonis is the ship between Sonic the Hedgehog and Chris Thorndyke.
 * Sonjet is the ship between Sonic the Hedgehog and Jet the Hawk.
 * Sonuckles is the ship between Sonic the Hedgehog and Knuckles the Echidna.
 * Metonic is the ship between Sonic the Hedgehog and Metal Sonic.
 * SonMario is the crossover ship between Sonic the Hedgehog and Mario.
 * Sonourge is the ship between Sonic the Hedgehog and Scourge the Hedgehog.
 * Sontails is the ship between Sonic the Hedgehog and Miles "Tails" Prower.
 * Sonoa is the crossover ship between Sonic the Hedgehog and Klonoa.
 * MegaSonic is the crossover ship between Sonic the Hedgehog and Mega Man.
 * Sonake is the crossover ship between Sonic the Hedgehog and Solid Snake.
 * Sonfinite is the ship between Sonic the Hedgehog and Infinite.

Polyships

 * Sonadilver is the ship between Sonic the Hedgehog, Shadow the Hedgehog and Silver the Hedgehog.
 * SonShadAmy is the ship between Sonic the Hedgehog, Shadow the Hedgehog and Amy Rose.
 * SonSalAmy is the ship or love triangle (where Amy and Sally are the two competing) between Sonic the Hedgehog, Sally Acorn and Amy Rose.

Non-binary

 * SoNiGHTS - the ship between Sonic the Hedgehog and NiGHTS.

Cargo Ships

 * SonChili is the ship between Sonic the Hedgehog and a chili dog.

Canon Relationships
As he appeared in all canons, Sonic could be the character with a large history of love interests in the series.

Fanon
As Sega's mascot and one of the key reasons for the company's success during the 16-bit era of video game consoles, Sonic is one of the most famous video game characters in the world. Also Sonic has been acknowledged as, undoubtedly, the most recognizable and famous character in the Sonic the Hedgehog franchise according to an official popularity poll.

In terms of shipping, as the main character of the series, Sonic is the most shipped character in the Sonic fandom, and it's pretty popular to see him paired with Amy, Sally, Blaze, Shadow, or even with crossover characters.