One cannot help but compare Jolteon to Raikou, its fellow fast special attacking Electric-type. At face value, Raikou seems the superior choice, as it has superior bulk and access to an excellent boosting move in Calm Mind. However, Jolteon has three main niches over Raikou. The first one is its superior base 130 Speed stat, which allows Jolteon to either plough through any Dugtrio moronic enough to switch in on Hidden Power, or evade its trapping by Baton Passing out of it. The second is its ability to Baton Pass Substitutes to powerful attackers such as Blaziken and Tyranitar, or just "dry pass" to an appropriate counter on a predicted switch. The third niche is its excellent ability, Volt Absorb, which allows it to switch in on Electric-type attacks with impunity and recover off them, which slightly increases its longevity throughout the game.
A major difference between the pair is that while Raikou is a comparatively poor lead—Blissey can switch in freely and give the opponent an advantage—Jolteon is an excellent lead that can keep your team's offensive momentum going by Baton Passing Substitutes. Jolteon is not bereft of flaws though, as it is vulnerable to all forms of status, Spikes, and sandstorm's residual damage; it is also very frail. These negative attributes mean that Jolteon is worn down quickly in slow-paced games.
This set is great at forcing switches, scouting the opponent's team out, and keeping offensive momentum, and as such, is very deserving of a slot on balanced and offensive teams. Thunderbolt is the obligatory STAB move of choice as it hits many Pokemon hard. The choice of Hidden Power is based around which threats your team needs to cover. Hidden Power Grass destroys Swampert, a driving force in the Advance metagame. Hidden Power Ice, on the other hand, creates a pseudo-BoltBeam combo, ploughs through Flygon, and takes a decent chunk out of Celebi and Venusaur, which forces the former to use Recover and quickly wears down the latter.
Baton Pass is what differentiates Jolteon from Raikou. While Raikou is stopped cold by special walls, such as Snorlax and Blissey, and is forced to switch out by them, Jolteon can simply create a Substitute on a predicted switch and Baton Pass it to a powerful physical or mixed attacker, which keeps the team's momentum going. Jolteon functions at its best in the lead slot. The reasons for this are not only because it can put pressure on the opponent, but because it will often be difficult to get Jolteon in mid-game without it sustaining heavy damage of some sort while switching in.Team Options & Additional Comments >>>
While Jolteon does not have the bulk to phaze reliably, it can make some use of Roar thanks to its ability to force switches as an offensive pivot. With Spikes support, Roar Jolteon can wear down the likes of Snorlax on predicted switches and weaken it to the point where Jolteon can take it out and sweep. Roar Jolteon can also act as an effective check to Calm Mind Raikou, as most Raikou users will stay in and boost. Jolteon has access to Wish, but Vaporeon and Umbreon are more suited to this job thanks to their higher bulk and lower Speed. Jolteon can also Baton Pass Speed boosts with Agility, which can support a powerful but slow sweeper such as Swords Dance Marowak. However, to pass on Agility boosts, Jolteon will either have to forgo Substitute or Hidden Power.
Toxic can be used to hit Swampert on the switch, which frees up a moveslot for Jolteon to use Hidden Power Ice to take down threats such as Flygon and Salamence. Jolteon has access to Thunder Wave, but this is fairly useless as nearly all of its counters are either immune to it (Flygon, Swampert, Camerupt, and Steelix), have the Natural Cure ability (Blissey and Celebi), or are slow and hence don't mind paralysis (Snorlax). Finally, Jolteon can use Tickle or Charm on the switch to take the punch out of attacks from Snorlax, Flygon, and Swampert. All in all, however, Jolteon's movepool is not particularly large, and it is probably best to stick to the listed set.
Checks and Counters
Jolteon is difficult to counter in the traditional sense as there are very few ways to stop it from doing its job. Steelix gets a special mention for being one of the few Ground-types that is not weak to either Hidden Power Ice or Hidden Power Grass, while Swampert works against Jolteon that lack Hidden Power Grass; both can also use Roar to force Jolteon out.
However, Jolteon has a multitude of checks. It can't do much to special walls such as Blissey, Regice, and Snorlax, but all three can do little to prevent Jolteon from Baton Passing Substitutes. Raikou can set up with Calm Mind on any Jolteon lacking Roar, and can even use Roar itself to prevent SubPassing. Flygon easily walls Jolteon that carry Hidden Power Grass, but Flygon and Swampert should first scout out Jolteon's Hidden Power of choice through smart switching; the latter can use Protect to do so as well. Defensive Grass-types, such as Celebi and Venusaur, do an excellent job at checking Jolteon as they resist Thunderbolt and take little from a weak Hidden Power. Furthermore, both have recovery, and as such prove a constant thorn in Jolteon's side. Porygon2 and Gardevoir are both excellent checks to Jolteon, as Trace lets them copy Volt Absorb and their high Special Defense stats enable them to wall Jolteon to no end.