SSBM items and SE4 equivalents:
Barrel Cannon - Wormhole beam with medium range
Barrel - Launches Drones?
Home Run Bat - Almost guaranteed one shot kill, range 1, very slow reload
Bob-omb - Long range torpedo, + to hit from area of effect, self destruct, Armor ability (hit first)
Bunny Hat - Afterburners
Capsule - Launches Mines?
Cloaking Device - Duh.
Also gives emissive armor ability and defense bonus.
Crate - Launches Satellites?
Egg - Emergency movement
Fan - Short range, weak but quad to shields, with + to hit due to rapid fire
Fire Flower - Damages only weapons, medium range
Flipper - Short range torpedo with the wormhole beam effect
Food - Emergency supplies
Freezie - Damages only engines, long range
Green Shell - Basic torpedo, very long range
Hammer - Short range, high damage, gives emissive armor ability but penalty to defense
Heart - Lots of emergency energy
Beam Sword - Medium range, fairly high damage, + to hit from quick speed
Lip's Stick - Lays mines?
Maxim Tomato - Lots of emergency supplies
Metal Block - Emissive armor, - to attack, - to defense
Mr. Saturn - Long range fairly weak torpedo
Super Mushroom - + to attack, - to defense
Parasol - Short range weapon with Crystalline Armor ability
Party Ball - Launches EVERYTHING except fighters!
Pokeball - Launches Fighters (Pokemon)
Poison Mushroom - - to attack, + to defense
Motion Sensor Bomb - Cobalt Warhead
Ray Gun - Long range repulsor beam
Red Shell - Basic seeker
Screw Attack - Short range low damage weapon with large + to hit and also a + to defense
Star Rod - Long range projectile weapon
Starman - Shield Generator
Super Scope - Long range, almost guaranteed one shot kill, VERY slow reload!
Warp Star - Engine that can be fired as a medium range weapon with - to hit
I imagine that characters' special attacks would also be components, albeit ones that can only be scale mounted on that character.