Most people run hasty/naive with 252 speed and varying investment from 252 atk to 252 satk based on the moveset you want to run.
Unless you mean espeon, in which case the calm mind and support set both can run 252 health.
So I guess you could say I'm pretty good at monotype.
The finals from a monotype room official tournament.
http://replay.pokemonshowdown.com/monotype-327358227
On an uinnvested espeon: only if you're lucky + the Espeon has taken some damage (spikes or otherwise).
On a health invested Espeon: only if your opponent is sacrificing his Espeon.
Pikachu is fully capable of getting a 1HKO on Gyarados with any useful electric move, Thunderbolt, Thunder, or Volt Tackle. There are very few situations, though, where a Pikachu can defeat an Espeon though, you'll need a specially defensive poke for that.