Green Fireball

A Green Fireball is Luigi's trademark element in most spin-off games. It is usually functionally identical to Mario's Fireball.

Other elements Luigi can use, however, include electricity as seen in Mario & Luigi: Superstar Saga and Mario Strikers Charged, whirlwinds as seen in Mario Super Sluggers, and Ice Balls as seen in Mario Kart Arcade GP DX for Ice Luigi and as a customization move for Luigi in Super Smash Bros. for Nintendo 3DS and Super Smash Bros. for Wii U.

Mario Bros.
Green Fireballs first appear as obstacles in Mario Bros., where they randomly appear on one side of the stage and move towards the other side.

Super Mario World television series
A Green Fireball appears in the Super Mario World television series episode "The Wheel Thing", representing the green-light signal in the fire traffic lights. When Mega Mechanasaur passes the traffic lights without stopping from the lit-up red fireball, the green fireball along with the red and yellow ones get shot out towards Mega Mechanasaur, breaking off its arms.

Super Smash Bros. series
Green Fireballs make their debut in the Super Smash Bros. series as Luigi's standard special move. The move is called Fireball, the same name as Mario's move, but it floats rather than bounces and does slightly more damage. Kirby can use Green Fireballs if he copies Luigi's ability. Luigi retains this standard special move in the rest of the Super Smash Bros. series, receiving no major changes. Metal Luigi in Super Smash Bros. Melee also uses Green Fireballs during his boss fight alongside Metal Mario.

In Super Smash Bros. for Nintendo 3DS and Super Smash Bros. for Wii U, the Green Fireballs can be altered into either Bouncing Fireball or Ice Ball, provided that they are unlocked first. Bouncing Fireball is affected by gravity, 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.

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. They are one of the only two Special Items that cannot be obtained by King Boo or Petey Piranha, the other being the Birdo's Egg. If a green fireball hits 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.

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. It always scores if it is shot inside the 3-Point line. When shot outside the 3-Point line, a teammate must complete the move, and it is not guaranteed the shot scores.

New Super Mario Bros. Wii
Green Fireballs make their Super Mario series debut in New Super Mario Bros. Wii. In World 5-Tower, Iggy Koopa shoots Green Fireballs from his magic wand to attack Mario and co. The speed of these fireballs are the fastest in the game, along with Morton's.

When Mario and co. encounter Iggy again in the World 5-Castle, he still shoots Green Fireballs from his magic wand, although not as fast as in his first battle.

New Super Mario Bros. 2
Green Fireballs reappear in New Super Mario Bros. 2, where Iggy's magic wand once again shoots Green Fireballs, much like in New Super Mario Bros. Wii.

New Super Mario Bros. U / New Super Luigi U / New Super Mario Bros. U Deluxe
Green Fireballs once again return in New Super Mario Bros. U, New Super Luigi U, and their Nintendo Switch ports. This time, Iggy waves his wand and shoots three fireballs while standing on the ceiling, some being his usual green flames, and some instead being red orbs that generate Magmaarghs when they land into the lava below.

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 in 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

 * Due to palette limitations in the NES version of Super Mario Bros. 3, Fire Mario and Luigi's fireballs appear green inside Toad Houses.