So I played around with this quite a bit and found it working exceptionally well, and is a boatload of fun to boot. Currently Yawn is only mentioned in OC, but I believe it needs its own set.
Analysis
QC Accepted: 3/3
Grammar: 2/2 [Fatecrashers, Snorlaxe]
[SET]
name: Yawn
move 1: Yawn
move 2: Protect / Substitute
move 3: Thunderbolt
move 4: Hidden Power Grass / Hidden Power Ice
item: Life Orb / Leftovers
nature: Timid
evs: 252 SpA / 4 SpD / 252 Spe
[Set Comments]
<p>Although a respectable force in OU, Jolteon is often quickly shut down by Blissey, or other Pokemon who resist or are immune to his attacks. This set aims to avoid being put in an awkward position by forcing the opponent to fight Jolteon with their secondary checks. The strategy is simple, force a switch using Jolteon's offensive presence and use Yawn on the switch-in. Normally, this will be a faster, Choice Scarf-equipped Pokemon aiming to gain momentum or KO Jolteon. Use Protect after Yawn to block any attacks. If, instead of Protect, you are using Substitute, only use it if Jolteon is faster than your opponent's Pokemon. If Jolteon is slower, switch out. Substitute is particularly useful if your opponent switches a second time to avoid falling asleep from Yawn. If your opponent stays in, however, they will fall asleep and be easily taken advantage of by Jolteon or one of your otherPokemon. Teams only tend to carry one solid check for Jolteon, so if said check gets slept, Jolteon's usefulness increases tenfold.</p>
[Additional Comments]
<p>Yawn and Protect form the sleep-inducing combo that is key to this set, while the rest of Jolteon's moves are dedicated to capitalizing on his good power and coverage. Thunderbolt is the obligator STAB attack, while Hidden Power Grass is used to hit Swampert. Hidden Power Ice can be used instead to hit Flygon and Gliscor, but it is often better to let another one of your Pokemontake advantage of these sleeping foes instead of going for the kill. The EVs are as simple as can be, with investment focused in Special Attack and Speed, as is standard for most Jolteon. Though all variations of Jolteon are made more potent with entry hazard support, this set becomes especially destructive. Yawn will undoubtedly force many switches, racking up entry hazard damage and enabling a clean late-game sweep. Baton Pass can be used to switch to an appropriate counter to whomever your opponent switches in. This is especially useful if Jolteon can safely set up a Substitute. Shadow Ball can be used over Hidden Power to hit Rotom-A for decent damage, but it is often not worth the loss in coverage. Another option is Wish, but due to Jolteon's general frailty, it is not recommended.</p>
<p>Dragonite makes a fantastic partner for this set. Choice Scarf Flygon is a primary check for Dragon Dance Dragonite, and with it fast asleep, Dragonite is free to sweep. Jolteon can also easily eliminate problem Pokemon for Dragonite, such as Skarmory and, if using Hidden Power Grass, Swampert. Dragonite also has a handy immunity to Ground-type attacks, Jolteon's sole weakness. Lucario also benefits from this set's sleeping capabilities, though it lacks the type synergy that Dragonite and Jolteon possess. Jolteon can put Hippowdon to sleep, who would otherwise reliably check Lucario. As with every Jolteon set, Blissey utterly walls it. As if to make matters worse, Blissey also has Natural Cure to get rid of sleep as it switches out. Blissey can be dealt with by powerful Pursuit users such as Scizor and Tyranitar. If using Hidden Power Ice, Swampert will cause some problems, even if it gets put to sleep. RestTalk Rotom-A can also absorb sleep and is not 3HKOed by any of Jolteon's attacks.</p>

Analysis
QC Accepted: 3/3
Grammar: 2/2 [Fatecrashers, Snorlaxe]
[SET]
name: Yawn
move 1: Yawn
move 2: Protect / Substitute
move 3: Thunderbolt
move 4: Hidden Power Grass / Hidden Power Ice
item: Life Orb / Leftovers
nature: Timid
evs: 252 SpA / 4 SpD / 252 Spe
[Set Comments]
<p>Although a respectable force in OU, Jolteon is often quickly shut down by Blissey, or other Pokemon who resist or are immune to his attacks. This set aims to avoid being put in an awkward position by forcing the opponent to fight Jolteon with their secondary checks. The strategy is simple, force a switch using Jolteon's offensive presence and use Yawn on the switch-in. Normally, this will be a faster, Choice Scarf-equipped Pokemon aiming to gain momentum or KO Jolteon. Use Protect after Yawn to block any attacks. If, instead of Protect, you are using Substitute, only use it if Jolteon is faster than your opponent's Pokemon. If Jolteon is slower, switch out. Substitute is particularly useful if your opponent switches a second time to avoid falling asleep from Yawn. If your opponent stays in, however, they will fall asleep and be easily taken advantage of by Jolteon or one of your otherPokemon. Teams only tend to carry one solid check for Jolteon, so if said check gets slept, Jolteon's usefulness increases tenfold.</p>
[Additional Comments]
<p>Yawn and Protect form the sleep-inducing combo that is key to this set, while the rest of Jolteon's moves are dedicated to capitalizing on his good power and coverage. Thunderbolt is the obligator STAB attack, while Hidden Power Grass is used to hit Swampert. Hidden Power Ice can be used instead to hit Flygon and Gliscor, but it is often better to let another one of your Pokemontake advantage of these sleeping foes instead of going for the kill. The EVs are as simple as can be, with investment focused in Special Attack and Speed, as is standard for most Jolteon. Though all variations of Jolteon are made more potent with entry hazard support, this set becomes especially destructive. Yawn will undoubtedly force many switches, racking up entry hazard damage and enabling a clean late-game sweep. Baton Pass can be used to switch to an appropriate counter to whomever your opponent switches in. This is especially useful if Jolteon can safely set up a Substitute. Shadow Ball can be used over Hidden Power to hit Rotom-A for decent damage, but it is often not worth the loss in coverage. Another option is Wish, but due to Jolteon's general frailty, it is not recommended.</p>
<p>Dragonite makes a fantastic partner for this set. Choice Scarf Flygon is a primary check for Dragon Dance Dragonite, and with it fast asleep, Dragonite is free to sweep. Jolteon can also easily eliminate problem Pokemon for Dragonite, such as Skarmory and, if using Hidden Power Grass, Swampert. Dragonite also has a handy immunity to Ground-type attacks, Jolteon's sole weakness. Lucario also benefits from this set's sleeping capabilities, though it lacks the type synergy that Dragonite and Jolteon possess. Jolteon can put Hippowdon to sleep, who would otherwise reliably check Lucario. As with every Jolteon set, Blissey utterly walls it. As if to make matters worse, Blissey also has Natural Cure to get rid of sleep as it switches out. Blissey can be dealt with by powerful Pursuit users such as Scizor and Tyranitar. If using Hidden Power Ice, Swampert will cause some problems, even if it gets put to sleep. RestTalk Rotom-A can also absorb sleep and is not 3HKOed by any of Jolteon's attacks.</p>
[SET]
name: Yawn
move 1: Yawn
move 2: Protect / Substitute
move 3: Thunderbolt
move 4: Hidden Power Grass / Hidden Power Ice
item: Life Orb / Leftovers
nature: Timid
evs: 252 SAtk / 4 SpD / 252 Spe
Why this set deserves to be on site:
- Lures and dispatches Scarf Flygon and ground types like no other
- Teams usually only carry one check to Jolteon, which you can sleep
- Still hits extremely hard without Choice Specs
Additional Comments:
- Protect is to get the jump on Flygon: usually they will assume you are switching out and use U-turn. With substitute they will still U-turn out and lose the effects of Yawn. Protect blocks against U-turn completely, meaning that they will be slept.
- Hidden Power Grass can be used to hit Swampert, but you miss out on key Pokémon such as Flygon
- Leftovers can be used for the extra survivability, but the offensive nature of Life Orb is preferred.
- Entry Hazard support makes this set very potent: by itself it can shuffle the opponent's team, and then proceed to clean up with its great speed and power.
- Baton Pass can be used over Protect to gain momentum and allow other members of your team to set up on a Blissey switching in.
- Shadow Ball can be used over Hidden Power to hit Rotom-A, though the loss in coverage is generally not worth it
- Wish can be used to recover health.
Teammates and Counters:
- Dragonite makes a great partner - it's immune to Ground moves and appreciates scarf Flygon being neutered.
- Lucario works in a similar vein: Flygon can revenge kill it and it doesn't OHKO Hippowdon. With these Pokémon slept using Jolteon, it can KO them / use Swords Dance again / whatever, it beats them.
- Blissey, as always, makes a showing as a Jolteon counter. This is especially apparent when using Yawn, as with Natural Cure it can easily switch out and be rid of the sleep.
- Swampert takes this on easily even when asleep if lacking HP Grass.
- Restalk Rotom-A can absorb the sleep and isn't 3HKO'd by any of Jolteon's moves.
name: Yawn
move 1: Yawn
move 2: Protect / Substitute
move 3: Thunderbolt
move 4: Hidden Power Grass / Hidden Power Ice
item: Life Orb / Leftovers
nature: Timid
evs: 252 SAtk / 4 SpD / 252 Spe
Why this set deserves to be on site:
- Lures and dispatches Scarf Flygon and ground types like no other
- Teams usually only carry one check to Jolteon, which you can sleep
- Still hits extremely hard without Choice Specs
Additional Comments:
- Protect is to get the jump on Flygon: usually they will assume you are switching out and use U-turn. With substitute they will still U-turn out and lose the effects of Yawn. Protect blocks against U-turn completely, meaning that they will be slept.
- Hidden Power Grass can be used to hit Swampert, but you miss out on key Pokémon such as Flygon
- Leftovers can be used for the extra survivability, but the offensive nature of Life Orb is preferred.
- Entry Hazard support makes this set very potent: by itself it can shuffle the opponent's team, and then proceed to clean up with its great speed and power.
- Baton Pass can be used over Protect to gain momentum and allow other members of your team to set up on a Blissey switching in.
- Shadow Ball can be used over Hidden Power to hit Rotom-A, though the loss in coverage is generally not worth it
- Wish can be used to recover health.
Teammates and Counters:
- Dragonite makes a great partner - it's immune to Ground moves and appreciates scarf Flygon being neutered.
- Lucario works in a similar vein: Flygon can revenge kill it and it doesn't OHKO Hippowdon. With these Pokémon slept using Jolteon, it can KO them / use Swords Dance again / whatever, it beats them.
- Blissey, as always, makes a showing as a Jolteon counter. This is especially apparent when using Yawn, as with Natural Cure it can easily switch out and be rid of the sleep.
- Swampert takes this on easily even when asleep if lacking HP Grass.
- Restalk Rotom-A can absorb the sleep and isn't 3HKO'd by any of Jolteon's moves.