Here is my competitive doubles team for my tournament this weekend

Gengar @ Lum Berry
Nature: Rash
Ability: Levitate
EVs: 252 SpAtt, 252 Speed, 4 Def
Moves:
Shadow Ball
Sludge Bomb
Curse
Rest

The point of my Gengar is to quickly curse whoever I see as the biggest threat and if I survive to the second term, I use rest and wake up with Lum berry and just work from there.

Jolteon @ Electric Gem
Nature: Rash
Ability: Volt Absorb
EVs: 252 SpAtt, 252 Speed, 4 Def
Moves:
Thunder
Thunderbolt
Signal Beam
Shadow Ball

Jolteon is my fastest pokemon and with Thunder and an electric gem, it's able to take out most pokemon in one shot. And with it's insane speed, it almost always goes first.

Kingler @ Ice Gem
Nature: Brave
Ability: Hyper Cutter
EVs: 252 Attack, 252 Def, 4 Speed
Moves:
Rock Slide
Crabhammer
X-Scissor
Ice Beam

My Kingler is my big attack pokemon. I found that when i battle Cresselia's they always use Light Screen so Kingler with X-Scissor is able to take care of that. Ice beam with ice gem is for those pesky dragons like Dragonite, Salamence, and Garchomp. His big flaw is any special move. His special defense is lacking as well as his speed so any electric attack or strong special attack is a one hit KO every time. Thinking of maybe going with a focus sash for his item to combat this.

Rhyperior @ Expert Belt
Nature: Mild
Ability: Solid Rock
EVs: 252 Attack, 130 defense, 136 Speed
Moves:
Rock Slide
Earthquake
Hammer Arm
Megahorn

My Rhyperior is my big basher. I expect him to go in, destroy maybe one pokemon and then have him get smoked by some special attack since, like kingler, that's his big weakness as well as his speed.

Arcanine @ Leftovers
Nature: Adamant
Ability: Intimidate
EVs: 252 Attack, 252 Speed, 4 Def
Moves:
Wild Charge
Flare Blitz
Extremespeed
Crunch

My Arcanine is suppose there to take out Grass, Ice, and Steel, which my team is potentially weak to. Extremespeed is there to take out those pokemon who may have low health. I gave him leftovers to help with the recoil damage from Wild Charge and/or Flare Blitz.

Scizor
Nature: Jolly
Ability: Swarm
EVs: 252 attack, 56 Defense, 200 Speed
Moves:
X-Scissor
Night Slash
Acrobatics
Iron Head

Scizor is here as a change of pace. His type is fairly unique and there isn't much super effective on him. He's got pretty good speed so he goes first often (assuming Jolteon or Gengar aren't on the field).

I also have other EV trained pokemon including Blaziken, Charizard, Porygon-Z, Chandelure, Magmortar, Dragonite, Salamence, Togekiss, Glaceon, Magnezone, and a Shuckle/Bronzong Power Trick/Trick Room combo. I was also considering training a Forretress with a Normal Gem and Explosion so that I could do a combo with Gengar and Forretress. If i should switch out any of these pokemon, let me know. Thanks