I guess I'll do NatDex/OU/NatDex AG for this.
NatDex AG:
Dracovish @ Choice Scarf
Ability: Strong Jaw
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Fishious Rend
- Crunch
- Outrage
- Earthquake
Why? Fishious Rend. Choice Scarf increases the probability that you'll go first. Strong Jaw boosts Fishious Rend and Crunch. Jolly boosts Speed. Fishious Rend doubles in power when you move first, is boosted by Strong Jaw, and is STAB. The strategy is to click Fishious Rend until you run out of PP/win the match/faint/face a Water Absorb Pokemon. Crunch is boosted by Strong Jaw. Outrage is STAB. Earthquake is just a great move in general.
OU:
Kingdra @ Choice Specs
Ability: Swift Swim
EVs: 252 SpA / 4 SpD / 252 Spe
Modest Nature
- Surf
- Draco Meteor
- Flip Turn
- Hurricane
Note: should be used in the rain. Kingdra is undeniably an incredible rain sweeper, with Swift Swim and Choice Specs. Modest boosts Special Attack, since in the rain you should be pretty fast anyway. Surf is STAB boosted by the rain. Draco Meteor is pretty strong STAB, and since you'll most likely be switching due to the Choice Specs, the Special Attack drop shouldn't be too bad. Flip Turn is for pivoting out of the Specs. Hurricane has 100% accuracy in the rain.
NatDex/OU:
Dragapult @ Choice Specs
Ability: Infiltrator
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Draco Meteor
- Fire Blast
- Shadow Ball
- U-turn
Dragapult also has a great offensive presence in OU. Choice Specs boost its Special Attack. Infiltrator allows it to bypass Substitute and screens. Timid is for a bit more Speed (since it gets enough of a Special Attack boost with the Choice Specs). Draco Meteor is STAB, and, once again, the Special Attack drop won't matter much since you'll be switching. Fire Blast hits Ferrothorn. Shadow Ball is STAB. U-Turn is for pivoting.
That's what I suggest, personally.
Hope this helps! :)