Rain Setter (Voltorb) @ Silk Scarf  
Ability: Static  
EVs: 252 Atk / 4 SpA / 252 Spe  
Naive Nature  
- Rain Dance  
- Taunt  
- Thunder  
- Explosion  
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Optional Move(s): 
- Thunderbolt
- Hidden Power [Water]
- Light Screen
Optional Item(s): 
- Magnet
- Lum Berry
Optional Ability: 
- N/A
Optional EV/IV(s): 
- 4 Atk / 252 SpA / 252 Spe (Naive/Timid Nature)
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Overview: Possessing the highest unboosted Speed in the tier and access to Rain Dance and Explosion makes Voltorb a one-dimensional but effective Rain setter.
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Rain Setter: Rain Dance allows Voltorb to set up Rain, providing support to teammates such as Seaking and Horsea. Explosion, boosted by Silk Scarf, removes Voltorb from the field as quickly as possible, preserving Rain turns, and threatens heavy damage on most targets. Taunt allows Voltorb to deny setup from other Pokemon, notably Spikes from Snorunt, Substitute from Ground-types such as Rhyhorn, and Sunny Day from setters such as Onix or Sunflora. Finally, Thunder is Voltorb's strongest STAB, and allows it to deal heavy damage to most neutral targets in the tier.
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Other Options: Thunderbolt is an option over Thunder as STAB that is not reliant on rain to hit. Hidden Power [Water] deals heavy damage to Ground-types attempting to tank its Explosion or Thunder, notably Rhyhorn, and is boosted by the rain. Light Screen is an option over Taunt to prolong the staying power of Voltorb's teammates. A spread with maxed out Special Attack over Attack, a Timid or Naive Nature, and holding a Magnet could be used to power up Voltorb's Thunder as much as possible, but Voltorb rarely is able to sweep and thus powering up its Explosion is usually more optimal as it wants to use it as quickly as possible. Opting for Lum Berry in place of Silk Scarf means that Voltorb is almost guaranteed to use Rain Dance and still have the opportunity to go for Explosion the next turn, although it will be slightly weaker. 
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Checks and Counters: Voltorb's frailty means that most threats that aren't weak to Thunder should be able to 1v1 Voltorb, though they must watch out for Explosion trading with them. Ground-types in particular are immune to Thunder and often have the bulk or resistances to tank Explosion. However, Voltorb's primary goal, to set up Rain, can't realistically be denied due to its Speed, and thus it has no true counters. However, it does reveal Rain-abusing teammates in the back, which makes it easier to play around them.
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