I'm just gonna cut to the chase here.
Nature: Timid (+Spe, -Atk)
Ability: Illusion (Comes in disguised as the last Pokemon in your party)
Item: Focus Sash
EVs: 4 Atk / 252 Sp. Atk / 252 Spe
I love this Pokemon. It comes in disguised as another Pokemon, so it has that element of surprise. Taunt makes sure no one can put in entry hazards (Stealth Rock, Spikes, etc.). Dark Pulse for STAB, Flamethrower for coverage (especially against Ferrothorn) and Extrasensory against Fighting-types if Zoroark is ever revealed.
Baton Passer- Gorebyss
Nature: Calm (+Sp. Def, -Atk)
Ability: Swift Swim (Speed increases if it's raining)
Item: White Herb (Returns any reduced stat back to normal once)
EVs: 252 HP / 24 Sp. Def / 232 Spe
Shell Smash is awesome. Sharply raises Atk, Sp. Atk and Spe. Unfortunately, it lowers both defenses. That's what the White Herb's for. Iron Defense raises Defense and Surf for STAB and so Gorebyss isn't Taunt bait. Baton Pass is to pass on the changes to a sweeper.
Revenge Killer/Scout- Scizor
Nature: Adamant (+Atk, -Sp. Atk)
Ability: Technician (Moves with 50 or less base power get a 50% boost)
Item: Occa Berry (Weakens any Fire-type attack once)
EVs: 8 HP / 252 Atk / 248 Spe
Bullet Punch and Pursuit get a boost from Technician and the former is a STAB priority move. The latter's power is doubled when a Pokemon switches out, making no one switches out with impunity. Superpower is for Steel-types, especially Heatran, Magnezones with HP Fire and Ferrothorn. U-Turn is for quick getaways.
Nature: Careful (+Sp. Def, -Sp. Atk)
Ability: Prankster (Gives +1 priority to all non-damaging moves)
Item: Leftovers (Restores some HP every turn)
EVs: 252 HP / 120 Def / 136 Sp. Def
Will-O-Wisp is to cause damage against anything that's not a Fire-type or has Guts. Taunt is to stop people from setting up anything against it. Recover keeps it alive, and Night Shade will always deal 100 damage, taking out most Pokemon in a few hits.
Physical Sweeper- Salamence
Nature: Naive (+Spe, -Sp. Def)
Ability: Moxie (Raises Attack 1 stage after every KO)
Item: Life Orb (Take some HP in exchange for powering up attacks)
EVs: 252 Atk / 4 Sp. Def / 252 Spe
Dragon Dance to raise Attack and Speed, Dragon Claw for a powerful STAB that doesn't confuse you (aka Outrage) and Earthquake and Fire Blast for coverage. Moxie raises Mence's Attack after every KO, making his attacks even stronger.
Special Sweeper- Gengar
Nature: Timid (+Spe, -Atk)
Ability: Levitate (Makes it immune to Ground-type attacks)
Item: Life Orb
EVs: 4 HP / 252 Sp. Atk / 252 Spe
~Hidden Power [Ice]
Shadow Ball for STAB and Giga Drain to take out Bulky Waters. Focus Blast for Ferrothorn and Dark-types and Wide Lens boost it's accuracy a bit. HP Ice gets rid of Flying- and Dragon-types.
So here you go. Make any adjustments you like. I'm trying to avoid using legendaries/Ubers, but if you want to add them in, go ahead. :)