PK Fire
From the Super Mario Wiki
PK Fire is an attack used by Ness in both Super Smash Bros. and Super Smash Bros. Melee. In the former, it is executed by pressing the B button alone. Once the foe is hit (or the ground is hit), it will burst into a miniature wild-fire, hurting anyone caught in it. When used in mid-air, Ness will fire it downward, instead of forward. It is best used as a rapid fire attack. In the latter, it was moved as Ness' Smash B move, and still had the same effect from the original. Not much has changed, except graphical improvement. It is interesting to note, Ness could never use PK Fire in Earthbound, along with PK Thunder, only Paula could. However, Paula's Trophy Bios hints that she probably taught Ness the attack.
In Super Smash Bros. Brawl, Ness, as well as his newcomer partner, Lucas, will be able to use PK Fire as well, acting as their side Special Move. Unlike Ness, who will fire the PK Fire downwards if he's in mid-air or near a ledge, Lucas always shoots the fire forward, even in mid-air. After the attack hits a player, or hits the ground, it will burst into a pillar of fire, causing more damage to anyone caught in it.
In the original Super Smash Bros. only, Kirby could use this attack when he copied Ness's powers.
