Alright, writing this up for Ninja Frog right here, bros!
Greninja (nicknamed ShadowFrog) Water/Dark Mystic Water
Awkward thing is that he has a tounge scarf. But whats good about him is the move Water Shuriken. Water Shuriken, like what fondanrt said, breaks through Sturdy. Its Dark Pulse is also good for pwning Ghost types. But he's probably not good on fighting Fairy types, or Fighting types.
Weakness: Grass, Electric, Fighting, Fairy, and Bug
Resistance: Fire, Water, Steel, Dark, Ice, and Ghost
Hawlucha (nicknamed Mysterio) Fighting/Flying Black Belt
Hawlucha is a powerful Pokemon that would pwn Steel types, and probably Rock types. Usually, people would choose Hawlucha over Talonflame, except some would pick Talonflame. I chose Hawlucha 'cause I need a Fighting type for those strong Normal types, and Steel types too. But, is it me, or every time I see Hawlucha, it reminds me of Mucha Lucha?
Weakness: Flying, Fairy, Electric, Ice, and Psychic
Resistance: Fighting, Bug, Grass, and Dark
Venusaur (nicknamed Junglesaurus) Grass/Poison Venusaurite
Venusaur is probably a good choice for a Grass type. He can help defeat Water types and Rock types, but with Fairy types, yeah. He can use Venoshock on them if he's Mega Evolved. But Venusaur fighting Gardevoir, bad choice. She'll pwn him with Psychic, which is not good.
Weakness: Ice, Fire, Psychic, and Flying
Resistance: Grass, Electric, Fighting, Fairy, and Water
Gardevoir (nicknamed Beauty) Psychic/Fairy Gardevoirite
Gardevoir is gonna be your best choice. She can pwn a Dragon type like a one-hit KO. She can be pretty handy for Ghost types, and Fighting types. She is not affected against Dragon, which is good. She can help you when you reach to the Pokemon League.
Weakness: Steel, Ghost, and Poison
Resistance: Psychic and Fighting
Heliolisk (nicknamed CapriSun) Electric/Normal Zap Plate
Heliolisk is good for those pesky Flying types. And also for Dragon types, if he has Dragon Tail, like he had in the anime, but his Flash will be perfect for lighting up caves. Whats awkward about him is that he can learn Surf, which is awkward for me, that I used Surf on my Greninja. Whats kinda epic for Heliolisk is that he can learn Dark Pulse.
Weakness: Fighting and Ground
Resistance: Electric, Steel, and Flying
Tyrantrum (nicknamed Megatron) Rock/Dragon Rocky Helmet
It'll be epic if he learns Draco Meteor, if his happiness is high. This is Game Freak's first try to make a Tyrannosaurus Rex, but whats handy is that he has Strong Jaws. What Strong Jaws does, is that it raises the power of biting moves (Crunch, for example), to 50%. Earthquake will do good, or Bulldoze for Clemont's gym, so that you can pwn your way to Clemont. But just Tyrantrum is total BEAST.
Weakness: Dragon, Fairy, Steel, Fighting, Ice, and Ground
Resistance: Normal, Flying, Poison, Fire, and Electric