This set is for Plusle/Minun sweepers in Single Battles.
Plusle/Minun @ Focus Sash
Ability: Volt Absorb
EVs: 252 Sp. Atk / 252 Spd / 4 HP
- Nasty Plot
- Grass Knot
- Signal Beam
It's not as absurd of an idea as it sounds. Okay, that's a lie. There are much better Pokémon suited for the job, like Earthquake Landorus. But your enemy will never see it coming and think of it as a joke, and start setting up. That's when you start setting up with Nasty Plot. As long as your enemy is slower than you, you can use your doubled/tripled/quadrupled Sp. Atk stat to use STAB Thunderbolt on pretty much everything. The Focus Sash is just a signal of when to go on the offensive.
If you run into a Ground type, they're either Primal Groudon or heavy. That's where Grass Knot comes in, as it's going to have about 120 power on most Uber ground types.
And Signal Beam is primarily for coverage against Psychic types, because they're annoying. Celebi resists Grass Knot which doesn't matter that much, but it resists Thunderbolt as well and that's one of the only reasons why you should run Signal Beam on this set.
Seriously, when you get to use this in Ubers, it gets stuff done.