Fireball

Fireballs are small projectiles launched by Mario and Luigi as their Standard Special Moves. Each travels a short distance, causing minor damage and flinching common to fire-based attacks. The ball's trajectory changes according to the stage's surface angle upon contact, though with different results for each character. Mario's ability to shoot fireballs provides the design justification for his other fire-based moves in the Super Smash Bros. series.

Fireballs were initially larger in Super Smash Bros., decreasing in size with Super Smash Bros. Melee and Super Smash Bros. Brawl. As with all Standard Special Moves, Kirby can also use Fireball after inhaling either brother.

Mario
Mario's Red Fireballs fall to the ground, losing momentum with each bounce. As such, they are more effective when fired from higher locations and toward downward slopes, traveling further. When firing at a wall or upward slope, the balls will bounce backward, a more defensive maneuver for brief protection from oncoming foes, perhaps in the air or from behind. Mario's Fireballs can be spammed, though with some difficulty, being fired at a slower rate of fire than Luigi's, but they are a decent approach tactic. The move can be more efficient when used in the air, falling to meet the enemy at ground level, while still moving, and negating lag.

In Super Smash Bros. for 3DS/Wii U, the move can be customized to the Fast Fireball, which is weaker but faster,or Fire Orb, which is slower but stronger.

Luigi
Luigi's Green Fireballs travel in a straight line and are unaffected by gravity, matching his floaty motif, and drift around in a circle, rather than rolling, like Mario's. Also, despite the fact Luigi's fireballs are green, they still make red-orange burn animations upon impact. They can be easily spammed, and can be fired at a slightly faster pace than Mario's, especially in the Negative Zone, Luigi's Final Smash. When firing at stage elements, the projectile's path will change based on the contact angle. As such, the move is more useful when used toward upward slopes, continuing on to foes. The move is more difficult to use on downward slopes, passing over enemies. Fireball approach is perhaps more difficult than with Mario, as the attack does not fall when used in the air. In general, Luigi's Fireballs are contextually less useful than Mario's, as they only travel in only one direction, where Mario's move in two. They also travel less distance, but deal slightly more damage than Mario's.

Fast Fireball
Mario's Fireball can be customized to become Fast Fireball in Super Smash Bros. 3DS/Wii U. Mario can launch fireballs which travel faster and at a longer distance, but do less damage. Funnily, this move is closer to how Mario throws fireballs in the Mario series.

Fire Orb
Mario's Fireball's other customization is Fire Orb. Mario throws a giant ball of fire which is very slow and gains little distance, but will hit opponents repeatedly for higher damage.

Bouncing Fireball
Luigi's Fireball can be customized to become Bouncing Fireball, which bounce on the ground like Mario's, but lose power with distance.

Ice Ball
Luigi's Fireball's other customization is Ice Ball, which is a frozen ball that travels very slowly. However, it can freeze opponents at higher percentages.