Originally Posted by Fat Scoopapa
If you don't wanna change any of the pokemon, Vappy could run toxic, which would let him beat Argonaut that don't run Rest. If they do rest, you could phaze them, or predict the rest and switch to Gem, to hit them with Energy Ball. Unfortunately, all of the moves on that set are pretty useful, so it would be difficult to decide which one to replace.
Nah, too many Arghonaut use Substitute to depend on Toxic as a solution. If Vaporeon wants to take on Arghonaut, HP-Electric is the best solution.