Green Fireball

A Green Fireball is a projectile and Luigi's trademark element in most spin-off games. Occasionally, it is functionally identical to Mario's Fireball.

Super Smash Bros.
Green fireballs are first attributed to Luigi in Super Smash Bros., appearing as his standard special move. The move is called Fireball, the same name as Mario's move, but it floats while drifting around in a circle, rather than bounces. Kirby can use green fireballs if he copies Luigi's ability.

Super Smash Bros. Melee
Green fireballs reappear as Luigi's standard special move and when Kirby copies his ability in Super Smash Bros. Melee. Metal Luigi can also use green fireballs during his boss fight alongside Metal Mario.

Super Smash Bros. Brawl
Green Fireballs reappear in Super Smash Bros. Brawl, where False Luigi in the Great Maze can also use them.

Super Smash Bros. for Nintendo 3DS / Wii U
Green Fireballs return in Super Smash Bros. for Nintendo 3DS and Super Smash Bros. for Wii U, where they can be altered into either Bouncing Fireball or Ice Ball via custom moves, provided that they are unlocked first. Bouncing Fireball is affected by gravity with each successive bounce decaying in height, much like Mario's Fireball, although Luigi takes more time to fire it. In comparison, Ice Ball has a chance of freezing opponents and has longer range, but deals slightly less damage and travels slower. When Kirby copies Luigi, he will always remains with Luigi's default standard special, even if Luigi has a set custom move.

As Master Shadow can copy characters and their abilities, he can also copy Luigi to shoot Green Fireballs as well.

Super Smash Bros. Ultimate
Green Fireballs return in Super Smash Bros. Ultimate, where Dharkon's Luigi clone can also use them in its boss battle in the World of Light.

Mario Kart: Double Dash!!
Green fireballs appear in Mario Kart: Double Dash!!, as Luigi's Special item and can be used only by him; not even Petey Piranha or King Boo can use it. It works similarly as Mario's Fireball item. When Luigi throws it either forward or backward, the green fireball splits into five and bounces around the course, which may ricochet off walls. The fireballs, when they hit any kart, including Luigi and his teammate's kart, cause the kart to spin out and the rear player is burned and momentarily stunned. If a green fireball hits a racer under the effects of a heart, the icon for the green fireball received is a red fireball.

As well as having the special item, Luigi has a personal kart, the Green Fire, unlocked once players beat Mushroom Cup on 50cc.

Mario Superstar Baseball
The Green Fireball, again simply known as the Fireball, is Luigi's Star Skill in Mario Superstar Baseball. When pitched with, the Green Fireball surrounds the ball with green fire and throws it as a fastball with very high velocity and little movement. Compared to Mario's equivalent Fireball pitch, it has slightly lower velocity and greater movement, matching Luigi's specialties as a pitcher. When batted with, the Green Fireball also surrounds the ball with green fire, hitting it as a ground ball to the infield. Players who attempt to catch the ball while it is lit are burned, stunning them for a short time.

In Challenge Mode with Mario, the player must purchase the Green Fireball item in order to enable use of this ability for Luigi.

Super Mario Strikers
Green fireballs are used in Super Mario Strikers. When Luigi or Yoshi uses their Super Strike, the ball will be encased in a green fireball while launching at the goal.

Mario Hoops 3-on-3
A Green Fireball is used in Mario Hoops 3-on-3, as Luigi's Special Shot known as the Green Fire Shot, identical to Mario's Fire Shot. When the player taps out the letter L on the touch screen, Luigi starts charging the ball with green fire. If he is not hit while charging it, he launches the ball to the basket.

Mario Sports Superstars
A Green Fireball appears in Mario Sports Superstars, as Luigi's special shot in baseball and soccer. When using his special shot, the ball is encased in a Green Fireball. Baby Luigi also uses a Green Fireball as his special shot in soccer only. In baseball, players who attempt to catch the ball in while it is lit are burned, stunning them for a short time.

Trivia

 * Despite the fireballs being green, they still make red-orange burn animations upon impact on a character.