Ryūken

Ryū-ken is Super Saiyan Goku's side special move in Super Smash Flash 2.

Overview
When performed, Super Saiyan Goku transforms into his Super Saiyan 3 form and then releases a long, golden dragon-shaped projectile from his fists. Once formed, the projectile travels straight forward and travels a very far distance before disappearing. Opponents hit by the head of the projectile are dealt 2% damage with weak knockback, while opponents hit by its body are dealt 10% damage with much stronger knockback.

There is no limit to how many projectiles can be on the stage at once, allowing Super Saiyan Goku to use the move consecutively with no risk. The projectile can also be caught in certain walls after being fully formed, leaving a lingering hitbox that can be used to attack opponents.

Origin
In the Dragon Ball franchise, the Ryū-ken, also known as Ryū-Ken Bakuhatsu or Chō Ryū-ken, is a very powerful attack and the only technique that Goku comes up with completely by himself. He begins the attack by making a straight fist faced at his enemy and then charging at them. Once his fist, along with his own body, exits the stomach or chest of the target, the energy he's built up will explode out into the form of an enormous golden dragon, which bears a great resemblance to the Shadow Dragon Eis Shenron, and then finally collides into the target, possibly destroying it in its path or leaving a gaping hole, hence the name "Ryū-ken".

Trivia

 * Prior to v0.8b of the SSF2 Demo, the player could not attack until after the projectile had left the stage boundaries.