Boost

The Sonic Boost (ソニックブースト) is a move used by Sonic the Hedgehog mainly in the games Sonic Rush, Sonic Rush Adventure, Sonic Unleashed, Sonic Colors and Sonic Generations (Modern Sonic). This move first appeared in Sonic Heroes, in the special stages where it can be used by all playable characters but since the release of Sonic Rush, it began to become one of Sonic's standard abilities.

Sonic Unleashed
The Sonic Boost officially appeared in Sonic Unleashed. To perform the Sonic Boost, the player has to fill the "Boost Bar" in the bottom-left corner of the screen. The bar can be filled by collecting rings, performing the Sonic Drift, or stringing together tricks and attacks (Wii/PS2 versions only). While performing the Sonic Boost, Sonic gains limited invincibility and increased speed, plowing through enemies and object/obstacles but he'll still get hurt from hazards such as spikes. The Sonic Boost is limited by the energy in the Boost Bar; in the 360/PS3 version, the Sonic Boost can be performed at almost any time, even if there is a little bit of energy in the bar. In the Wii/PS2 versions, the bar is divided into three sub-bars (upgrades can increase the sub-bars to a maximum of six) and can only be performed when at least one of the bars is completely full. This move can also be used to collect rings that are just out of reach, as the rings will be attracted to Sonic, much like the Lightning Shield. In the 360/PS3 there is also an upgrade found in Chun-Nan called the Air Boost Shoes (in the Wii/PS2 versions, Sonic already has all the upgrades). This upgrade can only be reached by also getting the Wall Jump Shoes in Spagonia. With the Air Boost Shoes, Sonic will be able to use the Sonic Boost in the air, as opposed to doing an ineffective Homing Attack.

Sonic Colors
This move reappears in Sonic Colors, and looks similar to the Wii/PS2 versions of Sonic Unleashed. In Sonic Colors, there is an effect seen to either side of Sonic, which also flashes in the colours of the rainbow. This effect is also seen when Drifting. Unlike in Sonic Unleashed, Sonic can only fill the Boost Bar by releasing White Wisps from Wisp Capsules or by defeating Egg Pawns.

Sonic Generations
The Sonic Boost also appears in Sonic Generations, the methods of using are the same as in Sonic Unleashed. To charge the Boost Bar, the player can defeat enemies, collect rings, drift, or perform tricks in the air. If enough tricks are performed, the Boost Bar can surpass it's actual capacity, allowing boost for a longer time than normal. In the rival battle against Shadow the Hedgehog, it is revealed that Shadow can also use Sonic Boost. When using boost, Shadow floats slightly off the ground, using fire from his Air Shoes to propel him forward, whilst using boost, Shadow is immersed in and orange and red aura. In the final cutscene for Sonic Generations, Classic Sonic jumps into the air and tries to perform boost, Classic Sonic achieves boost for a split-second, before losing it, causing him to fall to the ground. When Modern Super Sonic uses boost, he instead hovers at a blistering speed. However, the ring count drains up very quickly, as opposed to Sonic Colors.

Super Boost (Sonic Rush - Sonic Colors DS)
The Super Boost is a move utilized by Sonic the Hedgehog and Blaze the Cat in Sonic Rush and Sonic Rush Adventure. Closely related to the Sonic Boost from Sonic Unleashed the technique is activated by holding the X or Y button while on the ground. When the Tension Gauge has at least a little bit of energy, Sonic and Blaze can rush forward and plow through enemies while depleting the Tension Gauge. Once the Tension Gauge is maximally filled, the Super Boost can be used indefinitely for a limited time.

Mach Speed (Sonic the Hedgehog (2006))
Mach Speed sections are a feature exclusive to Sonic's gameplay in Sonic the Hedgehog (2006). The game engine itself drives Sonic forward at breakneck pace, leaving the player only in control of left/right movement and jumping. On a similar note, the blue gem upgrade for Sonic gives a small boost of speed.

Boost Mode (Sonic Advance 2)
Boost Mode refers, in its most general sense, to a high-speed dash state which some characters are able to perform, most notably Sonic the Hedgehog. The mode is accompanied by after-images of the character to emphasize the eye-blistering velocities involved.