Counter Shield

A Counter Shield is both an offensive and defensive battle maneuver developed by Ash Ketchum during his time in Sinnoh.

Concept
The basic idea behind the Counter Shield is that the Pokemon employing the maneuver is able to attack and defend at the same time. It shields the Pokemon from opposing attacks while simultaneously striking the opponent's Pokemon to inflict damage.

To perform a Counter Shield, a Pokemon rotates on its chest or back while using a non-physical attack, preferably along the lines of moves like Thunderbolt, Flamethrower, Aqua Jet and the like. The Pokemon's rapid rotation causes the move being used to spiral out in all directions forming a barrier which provides protection both from physical and energy-based attacks.

Background
When Ash battled Fantina, the Hearthome City Gym Leader, the latter's Ghost-type Pokemon kept putting his Pokemon to sleep using Hypnosis, presenting Ash with the twofold dilemma of having his Pokemon unable to land any hits while being vulnerable to opposing attacks as Fantina's Ghost Pokemon moved about. This difficulty plagued Ash for a while, and it wasn't until he saw his friend Dawn's participation in the Hearthome City Pokemon Contest that he gained an idea of how he could counter it.

The Counter Shield has two components, each of which were inspired by something Dawn did with her Pokemon:

1. An offensive move that inflicts damage and also blocks your opponent's attack. This came from seeing Dawn's Ambipom use Double Hit during her Pokemon Contest in Hearthome City.

2. Put the attack into a spin (meaning rotate). This is what enables simultaneous offense and defense. This first came about from seeing Dawn's Piplup and Buneary spin to avoid a rampaging Aerodactyl's Giga Impact. Ash later used this maneuver during his Gym Battle with Roark at the Oreburgh Gym. Before his Gym Battle with Fantina, Ash gave Dawn and Brock a demonstration of the then-unnamed Counter Shield by having Buizel perform the maneuver, which Dawn recognized as the spin from before.

Another reason this maneuver would prevent Hypnosis from working would be the Pokemon's rotation preventing it from making the necessary eye contact with the opponent's Pokemon.

Uses
When used by Ash against Fantina, the Counter Shield served three purposes:
 * 1) To protect his Pokemon against enemy attacks.
 * 2) To provide an almost-instantaneous counteroffensive.
 * 3) To restrict the movement of Fantina's Ghost-type Pokemon and prevent them from moving about, as this was the main problem Ash had while facing them.

Naming
The maneuver was christened "Counter Shield" by Fantina when she saw Ash's Buizel use it for the first time against her Gengar, "Counter" referring to the fact that Ash's Pokemon were counterattacking, and the "Shield" being for their defense.

Diamond and Pearl: Battle Dimension
During Ash's Gym Battle with Fantina, he pitted his Buizel, Chimchar and Pikachu against Fantina's Gengar, Mismagius and Drifblim.

Buizel vs. Gengar
Gengar went to use Hypnosis, but Buizel spun using Water Gun, negating the move and hitting Gengar. Fantina was surprised by this move and christened it "Counter Shield" as Buizel had attacked and defended itself. Gengar used Nightshade and Buizel used Water Pulse. Though both Pokémon got hit, Gengar got the thicker end and fainted.

Chimchar vs. Mismagius
Chimchar started with Flame Wheel, but even with the agility and speed, Mismagius stopped it with Psywave. Chimchar jumped and spun using Flamethrower as "Counter Shield". Mismagius used Psywave, but failed to as it still got hit by Flamethrower.

Pikachu vs. Drifblim
Pikachu used Thunderbolt, spreading the electricity and hitting Drifblim indirectly. Though paralyzed, Drifblim used Psychic to dispel it. Drifblim then used Will O' Wisp with Psychic to control it. Pikachu used Thunderbolt, but Drifblim's combination deflected the attack.

Buizel vs. Drifblim
Buizel spun using Aqua Jet, negating Drifblim's combination and hit it. Drifblim stopped it with Ominous Wind, so Buizel counterattacked with Water Pulse. Drifblim used Will O' Wisp to negate it and used the explosion to get close to Buizel and put it to sleep with Hypnosis and defeat it with Psychic.

Chimchar vs. Driflblim
Drifblim used Will O' Wisp, so Chimchar used Flame Wheel, but got stopped. Ash had an idea - Chimchar used Flamethrower, so Drifblim used its combination to attack. However, it fused with the attack and Drifblim got hit by it. Fantina didn't call it a victory yet and ordered an Ominous Wind. Chimchar dug into the ground to protect itself, then emerged from the other side, grabbed Drifblim and threw it on the ground. Drifblim went to use Hypnosis, but got hit by Flamethrower and fainted from it.

Ash vs. Paul
When Ash and Paul had their full six-on-six battle at Lake Acuity, the former's Pikachu faced off against the latter's Magmortar, using a Thunderbolt Counter Shield to deflect the other Pokemon's Smog. Buizel later used a Counter Shield to deflect Paul's Ursaring's Focus Blast right back at it, although this one resembled a cyclone instead of a barrier.

Ash vs. Paul - the Rematch
During their full six-on-six battle at the Lily of the Valley Conference, Paul's Gastrodon used a Muddy Water Counter Shield against Ash's Staraptor, suprising everyone at how Paul had adapted Ash's battle strategy. Later, Ash had his Buizel use a Water Gun Counter Shield to defend itself against an incoming Pin Missile attack from Paul's Drapion.

Black and White: Rival Destinies
Returning for a brief stint in Unova, Dawn's Piplup battled Cilan's Pansage. When Pansage used Rock Tomb, Dawn had Piplup spin using a BubbleBeam Counter Shield to use the Rock Tomb against them.

Variants
Only one known variant of the Counter Shield exists: in DP102: Shield with a Twist!, Fantina had her Drifblim combine its Will-O'-Wisp and Psychic to form what she called a "Counter-Counter Shield." This is the only known variant of the maneuver.

Trivia

 * Since its inception, the Counter Shield maneuver has been used against Ash twice: the first time was by Fantina in its debut battle (see above) and the second time was by Paul during the Sinnoh League in DP186: Familiarity Breeds Strategy!
 * Ash has yet to use a Counter Shield since its creation and development in Sinnoh.