Gyarados

[SET]
name: RestTalk
move 1: Rest
move 2: Sleep Talk
move 3: Waterfall
move 4: Roar / Dragon Tail
nature: Impish
item: Leftovers
ability: Intimidate
evs: 248 HP / 252 Def / 8 SpD

[SET]
name: Offensive Dragon Dance
move 1: Dragon Dance
move 2: Waterfall
move 3: Stone Edge
move 4: Earthquake / Bounce
nature: Adamant / Jolly
item: Life Orb
ability: Moxie / Intimidate
evs: 252 Atk / 4 Def / 252 Spe

[SET]
name: Bulky Dragon Dance
move 1: Dragon Dance
move 2: Waterfall
move 3: Taunt
move 4: Stone Edge / Bounce
nature: Adamant
item: Leftovers
ability: Intimidate
evs: 156 HP / 72 Atk / 96 Def / 184 Spe

[Other Options]

<p>On either of the Dragon Dance sets, there are several potential alternative items. Wacan Berry can allow Gyarados to survive a strong Electric-type attack and hopefully get in another Dragon Dance. Similarly, Lum Berry can be used to cure an untimely status effect, particularly a burn from Scald.</p>

<p>Aqua Tail can be used instead of Waterfall for a slight increase in power, but Waterfall’s perfect accuracy and chance to flinch the foe generally make it the superior option. Return is a viable coverage move, as the combination of Water and Normal is resisted only by Empoleon, Ferrothorn, Jellicent, and Shedinja in OU. Thunder Wave is a generally good move Gyarados can use, and lets it neuter checks that rely on Speed such as Rotom-W, Latios, and Latias.</p>

<p>A Choice Band set with Waterfall, Payback, Stone Edge, and Earthquake allows Gyarados to hit extremely hard right off the bat, but its vulnerability to the common sources of residual damage, Sandstorm and Stealth Rock, really hinders its survivability. Similarly, Gyarados can opt to run a Choice Scarf set with Moxie, but this set usually best left to Salamence due to Salamence’s higher base Speed and Attack.