Castform (Snowy)

Snowy Castform doesn't have the stats to be meta relevant at all, which is unfortunate because Weather Ball is such a good move. At least it has some niche use in PvP. 

Best PvE Offensive Moveset

• Powder Snow gets STAB and is the superior fast move.
• Tackle is underwhelming.
• Weather Ball Ice is a strong move as a 3-bar, and performs better than other options.
• Ice Beam has an advantage over Blizzard as a 2-bar move, but they're close in DPS. 

Best PvE Defensive Moveset

• Powder Snow doesn't deal a lot of damage on defense, but at least it has STAB. 
• Tackle is a bad move, but at least it leaves Castform a bit less walled out by anything resistant to Ice.
• Weather Ball Ice is the best charge move on defense due to it being a 3-bar move. 
• Ice Beam hits harder, but is used less frequently. 
• Blizzard might not be used before Castform faints, but could possibly KO an attacker. 

Powder Snow is the superior fast move due to its much faster energy generation, which lets Castform spam its powerful charge move.

Weather Ball can be used very frequently with only 35 energy cost, and deals considerable damage with STAB. This alone is enough for Castform simply due to how cheap and effective it is compared to its other charge moves. Since Castform lacks any coverage moves, it is not necessary to unlock a second charge move. Ice Beam and Blizzard cost too much energy for their damage; it's better to just spam Weather Ball.