Insta-Shield

The Insta-Shield, known as the W Spin Attack or W Kaiten Attack (W回転アタック) in Japan, also called the Wind Attack and Twin-Spin Attack, is a move used by Sonic the Hedgehog and Miles "Tails" Prower that first appeared in Sonic the Hedgehog 3. When using it, the playable character creates a rapid 360° spiral flashing around them for both offense and defense.

Description
When performing Insta-Shield, the user creates a temporary shield for a split-second that can slash enemies and items within their range without the player has to touch them. It can also be useful for defeating more defensive enemies and even avoiding projectiles. The Insta-Shield is usually performed by tapping one of the jump buttons while the playable character is in mid-air after already performing a Spin Jump.

Sonic the Hedgehog 3 & Knuckles
The Insta-Shield is first seen as one of new types of techniques for Sonic in Sonic the Hedgehog 3, and is featured in the same way in the add-on continuation Sonic & Knuckles and the lock-on Sonic the Hedgehog 3 & Knuckles. Sonic is able to create an Insta-Shield while Spin Jumping by pressing, or  again in mid-air, creating a temporary shield around him. It is useful when the player has to avoid and destroy small projectiles and defeat heavily armed enemies including Star Pointers or Orbinauts without touching them at all, however the player has to do this very close to the enemies or projectiles.

Tails and Knuckles can't use the Insta-Shield due to having their own abilities. The Insta-Shield cannot be used while Sonic is equipped with a shield in both games, while having Invincibility or while Super Sonic. Instead, he will perform an action depending on the type of shield possessed:
 * A Flame Shield will allow Sonic to perform the Fireball Spin Dash.
 * An Electricity Shield (also called a Lightning Shield) will allow Sonic to double jump.
 * A Water Shield will allow Sonic to slam downwards and bounce. Sonic can use this to increase his jump height slightly.
 * While in his hyper form, Sonic will perform the Hyper Flash.

Sonic Advance series
The Insta-Shield returns in all three Sonic Advance games (though it is called Spin Attack in Sonic Advance, Double Spin Attack in Sonic Advance 2 and Wind Attack in Sonic Advance 3) and is performed in the same manner as it is in Sonic the Hedgehog 3 & Knuckles. In first two games, only Sonic is able to perform the Insta-Shield by pressing  during a Spin Jump. He is also able to do it in Sonic Advance 2, but if the player is close to a normal Badnik, Sonic performs a Homing Attack instead but will be able to perform Insta-Shield afterwards.

In Sonic Advance 3, Sonic can only perform the Insta-Shield while having Knuckles as his partner by pressing  while jumping. Tails can also perform a variation of this move called the Tail Spin Attack in the same game while he is partnered with Knuckles.

Sonic Generations
In the console/PC version of Sonic Generations, the Insta-Shield is one of Skills only available for Classic Sonic under the name Twin Spin Attack. The skill is unlocked by collecting all the Red Star Rings in Sky Sanctuary Act 1 and costs 30 points to equip. The Twin Spin Attack functions similarly to how it did the in previous games, but the slash effect is more transparent than white. It is performed by pressing the / while jumping.

Sonic the Hedgehog (1991)
In the 2013 re-release of the original Sonic the Hedgehog, Sonic can perform the Insta-Shield if the player enables Debug Mode. Once in an act, if the player places two Monitors with the three elemental shields and destroys them both, the player will be able to perform the Insta-Shield (as long as he is not equipped with any Shields). If the player destroys two of the aforementioned Monitors again, Sonic can no longer perform the Insta-Shield until he smashes two of those Monitors again. The Insta-Shield retains the same appearance from Sonic the Hedgehog 3 & Knuckles.

Sonic the Hedgehog 2
In the 2013 re-release of Sonic the Hedgehog 2, much like 2013 re-release of the original Sonic the Hedgehog, Sonic can perform the Insta-Shield only via Debug Mode. In this game however, only one of the Monitor with the three elemental shields is required to be smash to alternate whether Sonic can perform the Insta-Shield or not.

Sonic the Comic
Sonic used the Insta-Shield (unnamed in this continuity) twice in issues of Sonic the Comic: first to protect himself from a Pointdexter in the Marble Garden Zone shortly after visiting the Floating Island for the first time, and again while fighting Knuckles. Sonic explained that he created the forcefield by vibrating the air molecules around him at super speed.

Archie Comics
In Archie's Sonic the Hedgehog comics, Sonic the Hedgehog has done Insta-Shield only once in comic issue 13. After crashing down on the Floating Island, one of Robotnik's flying machines starts attacking Sonic and Tails with a flamethrower and bombs. Sonic unknowingly manages to perform the Insta-Shield in time while dodging flames.