Pokémon X and Y Walkthrough, Pokémon Move Sets: Chesnaught
(Please note that the recommendations below are largely made for in-game play. A Chesnaught in a competitive environment will likely make use of different moves to accommodate for smarter, more adaptive opponents. Got a different moveset for this burly starter? Toss it in the comments.)
One of the three new starters in the sixth generation of Pokémon, Chesnaught is as much a bruiser as it appears. Less of an upper-tier generalist than many starters in the past, Chesnaught is statistically specialized. Consequently, it can prove to be virtually worthless against some opponents... and an absolute beast against others. Fortunately, the latter proves to be true more often than not.
Type: Grass / Flghting
Chesnaught starts off as the diminutive Chespin. Level this grassy starter to 16 to earn a Quilladin. Keep going to level 36 and you'll receive a Chesnaught for your trouble.
Dark, Electric, Grass, Ground, Rock, Water.
Fairy, Fire, Flying (4x), Ice, Poison, Psychic.
Chesnaught is, for the most part, not your standard starter pokémon statistically. In deference to its fighting-type division it has an outstanding Attack stat, only outshone by its even better Defense. HP is surprisingly high, and Special Attack and Special Defense are both average. Only Speed drops below the average line.
Overgrow: If the pokémon is reduced to one third of its total HP, its grass-type moved receive a boost to their attack power. Considering Chesnaught's defensive capabilities, you may wind up weak without getting knocked out a lot. Overall a pretty useful ability.
Bulletproof: The pokémon is immune to any ball- or bomb-based moves, such as Aura Sphere, Egg Bomb, Energy Ball, or Ostazooka. Bulletproof is largely useful for warding off Sludge Bomb, one of Chesnaught's worst nightmares. Handy! This is a hidden ability.
Chesnaught is, like most fighting-types, utterly reliant on physical attacks for doing damage. It has plenty of options in this sense, too, with Wood Hammer acting as a good STAB choice for its grassy side and Hammer Arm providing STAB coverage for its more martial side. Both are a teensy bit risky, particularly Wood Hammer with its recoil damage, so you make want to substitute in Seed Bomb and Brick Break instead. Outside moves to complete the set are myriad; I personally prefer Earthquake and Dragon Claw. Stick with physical moves only. If you didn't emphasize Attack in your EV training, give your Chesnaught Swords Dance to make up for the lack of hitting power.
Chesnaught also has the capacity to be a decent staller, so long as you work on its Special Defense. Your primary weapons here will be Toxic and Spiky Shield, both of which will slowly chip away at enemy pokémon. Spiky Shield is especially handy for warding off physically-dominant flying-type moves, which are Chesnaught's worst enemy by far. Leech Seed will keep your Chesnaught healthy, while at least one STAB move (in this case the safer Seed Bomb) provides coverage for those rare occasions where your opponent accidentally sends out the wrong type of pokémon. You may also want something that can increase Defense; Bulk Up is a decent choice.
EV / Super Training
There are two directions to go here. The first is to turn your Chesnaught into a defensive bruiser and emphasize its Attack and Defense. By pouring Defense EVs into the thing it will stand a decent chance of turning away flying-type attacks. On the other hand, you can pour your EVs into Special Defense and give your Chesnaught a better chance of surviving its other weaknesses, which are unfortunately myriad. Either way, don't worry too much about bulking up its other stats.
Catching a Chesnaught
Oh, those blasted starters. If you didn't choose Chespin as your first pokémon you'll have a second chance to get one at the end of the game, as Shauna will give you one after the credits roll... but only if you chose a Fennekin. Otherwise, you'll have to trade for one or hope you have a friend with Chespin in their Friend Safari.