Rain team based around a M Swampert

[GhettoPrimeape]

I would say if you Choose Plusle make sure it has Lightning Rod for that sp.atk Bonus ! With the Moveset:
Nasty Plot
Thunderbolt/Thunder (If its in rain,Thunder won't miss and has a Base 110 Sp.atk so thats really good.)
Grass Knot
Protect

But if you Pick Minun Go with the same moveset, But minun Special ability is Healing so you pick.

Hoped I helped.