Pokemon Part III

 Meowth should return again as a pokeball. Truth is, there's just too many Generation 1 pokemon, sorry Meowth

 Sudowoodo could use Mimic and copy an opponents move and fire back at them to give them a taste of their own medicine so to speak

 Octillery could use Octozooka and fire ink balls at an opponent while making a smoke effect to prevent anyone from seeing them

 Plusle or Minuin would appear by themselves, they would use a weak shock attack, but if both are on screen at the same time, they could KO all enemies on-screen.

Delibird could use Present and toss a present at the nearest opponent. It could either do damage, be a bomb, or recover health for that opponent

 Aerodactyl could use Rock Slide. He could fly over the screen dropping rocks on all opponents

 Miltank could use Rollout. I think she should be similar to Marill, though, shortly disappearing offscreen.

 Smeargle could use his signature Sketch. Whatever move the person who released used, Smeargle would "learn" and attack the opponent with that move several times.

 Hariyama could attack an opponent with Smellingsalt

Pineco could surround himself with Spikes, damaging any opponent who touches them

Pokemon Part II

Buffolant could charge up and use his signature Head Charge for major damage

 Unown could reappear like they did in Melee. Even though it's not a strong or popular pokemon, it's very unique and had a cool effect in Melee

Spheal could use Ice Ball and spit out a bit of ice at an opponent

Alakazam could use Kinesis and bend his spoons to grab an opponent mid-air for you to smash to pieces

 Lickitung could use...take a guess....yeah Lick

 Jynx could use Lovely Kiss to put an opponent to sleep

 Heracross could be a short-range but deadly force with his Mega Horn

 Hitmonlee could use Mega Kick like he did in the original Smash Bros.

 Hitmontop could use Triple Kick and spin around in a circle while kicking anything that touches it

Beedrill could reappear like Hitmonlee from the original Smash Bros. and swarm with twineedle

New Pokemon Part I

 Both Zekrom and Reshiram could use their signature moves, Fusion Bolt and Blaze Bolt

 Farfetch'd is a farfetch'd pokemon, who deserves a pokeball appearance. Maybe he could attack with his leek and use Aerial Ace

 Mr. Mime could create walls using Barrier and reflecting projectiles

 Substituting Blaziken in a pokeball would at least satisfy some fanboys. He could use Blaze Kick

 Marowak could use Bone Club and chuck his club like a boomerang

 Shellder could use Clamp and latch onto someone

 Krabby could use Crab Hammer and slam your enemies

 Diglett could use Dig and pop up to hit someone

Galvantula could use Electroweb to restrain someone