Ness's moves come from the game Earthbound and mainly revolve around the concept of telepathic powers, hence the names "P.K." (PSI in the English release of Earthbound meaning Psychic). Other than that Ness has his trusty baseball bat and yo-yo as smash attacks to eliminate opponents. These two items can be bought in the Earthbound game very early on.
Baseball Bat (Side+C)
Ness prepares for a hit and swings, causing massive damage and knock-back Yo-Yo (Up+C)
Shoots upwards and damages enemies. Great tool for juggling opponents in the air
P.K. Fire (Side+B)
Shoots forward and stuns enemies in the fire
P.K. Flash (Neutral+B
Can move forward or back and causes massive damage and knock-back
P.K. Magnet (Down+B)
Absorbs energy attacks and pushes opponents back a little