The Knuckle Slam is Knuckles the Echidna's Signature Move in Sonic Rivals 2. When using this move, Knuckles forms a field of shockwaves around him that damages all incoming obstacles. It replaces Knuckles' Signature Move, Hammer Punch, from Sonic Rivals.
Description[]
In order for Knuckles to use Knuckle Slam, he must have his Signature Meter completely filled, which can be done by collecting Rings, defeating enemies or boosting.
When executing the move, Knuckles jumps into the air and says "Knuckle Slam" while charging up energy. He then punches the ground with his fists, creating a large column of red energy. After this, a red field made of bursts of fire and minor exploding shockwaves surrounds Knuckles. This energy field will remain active for as long as there is energy in the Signature Meter, which begins to deplete once the Knuckle Slam is active. In gameplay, the player has to press the square button to activate this move. To slightly extend the duration of Knuckle Slam, the player has to repeatedly press 
.
Description of the Knuckles Slam
While the Knuckle Slam is active, any breakable obstacles, offensive Power-Up or Badniks in the stage that come into contact with the energy field surrounding Knuckles are instantly destroyed. The character that Knuckles faces off against throughout the stages in the games, however, instead takes damage as if they were hit by a normal attack, though the Knuckle Slam allows continuous damage.
As with every other Signature Move in Sonic Rivals 2, Metal Sonic can perform this ability when using his own Signature Move, Copycat, when racing against Knuckles.
In other media[]
Sonic Boom[]
In the Sonic Boom franchise, the Knuckle Slam appears in the game, Sonic Dash 2: Sonic Boom. Here, it is a special power of Knuckles the Echidna which can destroy Badniks.