It would work like Diddy Kong's Bananas. Pour up to two puddles around the stange, and anyone who steps on it trips and  falls.

Also, I think there should be skins of characters (kind of like how Wario had two different costume sets. This would get rid of some character clutter.

Mario (Paper Mario)
Luigi (Paper Luigi)
Princess Peach (Paper Peach, Princess Daisy)
Bowser (Paper Bowser)
Yoshi (Boshi)
Wario (Classic Wario)
Donkey Kong (Funky Kong)
King K. Rool (Captain K. Rool, Baron K. Roolstein)
Link (Shadow Link)
Ganondorf (Toon Ganondorf)
Toon Link (Young Link)
Samus (Dark Samus)
Zero Suit Samus (Gandrayda)
Ridley (Meta Ridley)
Fox (Falco)
Wolf (Leon)
Pikachu (Pichu, Raichu)
Zoroark (Lucario, Mewtwo)
JIgglypuff (Igglybuff, Wigglytuff)
Captain Falcon (Black Shadow)
Captain Olimar (Louie, The President)
Villager (Female Villager)
Marth (Roy)
The Black Knight (General Zelgius)
Ness (Lucas)
Snake (Big Boss, Old Snake)
Sonic (Shadow)

More 3rd party characters like Travis Touchdown(NMH), Mr. Ford(The Conduit), Mega Man, Ryu(SF), Teenage Mutant Ninja Turtles, Cecil from final fantasy 4, and keep Snake & Sonic. Nintendo should also add Little Mac and Saki.

Give Ganondorf his own damn moveset and I'm already satisfied.

Flint or Paula would also be appreciated.

I agree.Is nice to 1 or 2 to spice it up but the focus must be 99% Nintendo.

Ridley wouldn't fit in at all, people. He's far too large, (like, three times the size of Bowser) would look clumsy and stupid on the ground and just wouldn't fit in with the other fighters. Let's just be happy, that he's included as an unplayable character.

Anyways...

Likely:

Little Mac.

Another character from Pokémon. (Preferably Gengar or Alakazam, but I doubt, that they'll add any more gen 1 Pokémon to the fray.)

King K. Rool

Might get added:

Another Sonic character. (Knuckles or Shadow would probably have the most interesting movesets.)

Yarn Kirby

Wolf Link (Could be kinda like ZS Samus or Sheik.)

Unlikely, but would be pretty cool: 

Travis Touchdown

Mega Man

Simon Belmont

Characters, that I want removed from the game:

Jigglypuff

Ice Climbers

Most clone characters. Or at least give em' a moveset of their own. (Even though Ganondorf and Toon Link are my favorite characters.)

PROFESSOR LAYTON - MAKE IT HAPPEN OR I KILL EVERYONE

How about Anthony Higgs?  His taunt could be "Remember me?!?".

But honestly, speaking of 3rd party:

Viewtiful Joe, just because his move set would translate perfectly.

Travis Touchdown, Mega Man, and a Belmont would be nice too.

Yarn Kirby and Rayman would be cool.

I tend to hate seeing people suggesting 4 billion third party characters. They are fun to add, but too many and it will just make a mess of a roster. In some way, it may be better not to have them lest thin become Soul Caliber.

Outside of the obvious, I'd like to see Elza from the Last Story, Samurai Goroh and Toad. I think they'll all make great characters.

Pfft, you dare doubt Nintendo's ability to resize characters? Bowser's been all over the place (See: Sunshine. Still have no idea what happened there...).

He'd be a bigger bulkier MetaKnight as far as movement/jumping went. He'd have four "jumps" (flaps of wings like MetaKnight/Pit), and a gliding recovery special.

I'm guessing his stats would be something like this (out of five):
Size: 5 (even though he's shrunked down, he'd still be up there with Dedede and Bowser)
Weight: 4 (He's a skinny thing though, so he wouldn't be impossible to knock out. About Ike's weight)
Power: 4 (Claw slashes and tail sweeps for Smashes. And energy blasts for Specials.)
Speed: 2 (Slow and somewhat clumsy on the ground, but his wings allow him to traverse at a somewhat faster speed than the slowest of the slow.)
Jump: 4 (Right with King Dedede in jumping ability)

Ridley! Believe! (That was the NSider [official Nintendo forums] saying for Smash Bros. Brawl. )