These are all the Final Smashes for SSBB...
Mario: Throws a giant fire tornado

Yoshi: Grows wings and flies and shoots fire balls

Peach: Puts everyone to sleep and drops peaches that everyone can eat

Bowser: Transforms into Giga Bowser

Donkey Kong: Takes out the Donkey Kongas and starts playing

Diddy Kong: Gets his barrel jet packs and peanut launchers

Wario: Transforms into Wario Man

Pikachu: Uses Volt Tackle

Pokemon Trainer: Uses Triple Finish (Squirtle uses Hydro Cannon, Ivysaur uses Frenzy Plant, and Charizard uses Blast Burn)

Pit: Calls on warriors to help

Samus: Shoots a giant laser beam but looses her armor

Zero Suit Samus: Transforms into Samus

Kirby: Throws everyone in a cooking pot and cooks them

Meta Knight: Shrouds the field in darkness then cuts with his sword

King Dedede: Calls on his minions to help

Link: Slashes at his enemy with the Master Sword

Zelda/Sheik: Shoots a Light Arrow

Falco: Calls upon a Landmaster

Ice Climbers: Create a huge iceberg

Olimar: Goes on his rocket while monsters attack then the rocket drops back down

Ike: Throws his enemy into the air and slashes at them

Lucas: Calls upon a meteor storm

Ness: Same as Lucas

Luigi: Covers part of the stage in the negative zone, which has various side effects

Captain Falcon: Runs the enemy over in his racecar

Snake: Gets in a helicopter and shoots a grenade launcher

R.O.B.: Shoots a laser beam

Sonic: Transforms into Super Sonic

Game and Watch: Transforms into a octopus

Fox: Same as Falco

Lucario: Uses Aura Storm

Jigglypuff: Expands

Ganondorf: Transforms into the pig form from Twilight Princess

Marth: Shoots his enemy into the air