Hammer Punch

The Hammer Punch is a technique used primarily by Knuckles the Echidna, and later, by extension, Metal Sonic. When using this technique, the user throws a particularly powerful punch into the ground that causes wide tremors that which disables the opponent.

Description
When performing the Hammer Punch, the user jumps into the air and then strikes the ground with a extremely powerful punch, with the user's fist, on the way down, with enough force to trigger a large tremor throughout the area that the user is located in, be it the air or on the ground. The shakes from the tremors will then cause the opponents with the Hammer Punch's area to lose their footing, leaving them disorientated or stunned.

Sonic Adventure 2 and Sonic Adventure 2: Battle
The Hammer Punch first appeared in Sonic Adventure 2 and later in its remake Sonic Adventure 2: Battle where it was only used by Knuckles the Echidna. Unlike most of Knuckles' other techniques, however, he cannot Hammer Punch perform in the Story Mode. However, he can perform it in the game's two-player mode where two players races each other in a hunt to collect most of the Master Emerald's Emerald Shards, but only if he has collected enough rings.

Gameplay-wise, in order to allow Knuckles access to the Hammer Punch technique in two-player, he must have collected at least 20 rings. As soon as he has done that, he can use hammer Punch unrestrained. When performing the Hammer Punch, Knuckles shouts "Get down", before striking the ground. The tremor caused by the Hammer Punch will then cover the entire stage, striking the opposing player's character wherever he/she may be. Though the opponents' character does not take damage from the Hammer Punch, it will cause him/her to trip and be left dazed and disorientated for a short while, scrambling up the other player's controls over the said character. If the opponents are climbing while the Hammer Punch is performed they will be knocked off the walls. However, if the opponents are gliding while the Hammer Punch is performed, it will have no effect.

Sonic Rivals
The Hammer Punch returned in Sonic Rivals, though its execution was displayed in a far more powerful manner. In order for Knuckles to use the hammer Punch in this game, he must have his Star Item/Signature Meter completely filled, which can be done by collecting rings or defeating enemies. When Knuckles then performs the Hammer Punch, he will shout "Hammer Punch" and strike the ground with such force that it triggers a wide eruption, with large columns of fire erupting from the place where the punch was struck. The opponent then would then be stunned in his tracks for a short while, be it on the ground or in mid-air, regardless of where he would be located in the stage. In gameplay, the player has to press the triangle/square button to activate this move.

As with every other signature move in Sonic Rivals and Sonic Rivals 2, Metal Sonic can perform this ability when using his own signature move, Copycat.

Trivia

 * In all of its appearances, the Hammer Punch can only be used when special circumstances are fulfilled.