Hop

Hop is a move used by Amy in the first Sonic Advance game and later adapted by Sonic the Hedgehog in the main game series since Sonic Unleashed. It is a small leap Sonic does while running to avoid small bumps during the courses, while allowing him to preserve the momentum of his speed.

Description
Hop involves Sonic jumping with a lightly leap without going into a full Spin Jump. It can be used to quickly cross small gaps and clear low obstacles that would otherwise make Sonic trip, negate his Sonic Boost technique and slow him down, without losing speed and/or momentum, which is the downside of using a regular Spin Jump.

Sonic Advance
The hop is Amy's move used to build momentum in place of the Spin Dash it can be linked into a Head Slide to damage foes.

Sonic Unleashed
Sonic can hop starting from his first "modern" Sonic game. It isn't really needed, though.

Sonic Colors
The Wii version of Sonic Colors allows Sonic to hop by lightly tapping the jump button. It isn't ever required, however, and is simply a novelty.

Sonic Generations
The hop is given more of a use in Sonic Generations. Special, brightly colored, long bumper-style objects can be found in several modern zones, including Green Hill and Speed Highway. If Sonic collides with one without hopping, he will still go over it, but will lose almost all momentum and speed. Hopping allows Sonic to quickly cross these obstacles, something the game points out in Green Hill.

The 3DS version of the game is the first portable game to allow Sonic to hop; however, like in Unleashed and Colors, it is simply a novelty that can easily be entirely ignored.