Ok, so this is a team I have thought about recently and have used it in a few battles to great success so far (apart from the times I have made a mistake :p, but I sitll havent lost with it). It started off based around lead metagross and branched out into an offensive team, well mostly offensive.
There are a couple of pokemon here to keep the others alive or my opponents down.
Metagross: Leftovers
Adamant nature 252HP 236Atk 12Def 8Spd
Meteor Mash
Bullet Punch
Stealth Rock
Explosion
Ok so this is the lead and pokemon that started this team off. His main aim is to get the rocks up, damage as many pokemon as possible and then detonate and take someone with him. Explosion I find very useful for taking down a pokemon that is threatening my team and is being a right pain in the arse to take down. Meteor mash is over earthquake because I have yet to encounter a lead (me personally) that gets hurt more by earthquake than meteor mash, and the occasional attack rise is helpful.
Alakazam: Choice Specs
Synchronize
Timid Nature: 252SpAtk 252Spd 6HP
Psychic
Signal Beam
Focus Blast
Trick
My first sweeper, the ability to trick specs onto other pokemon was the main reason I picked Alakazam over other special sweepers, since he can cripple tanks/walls or anyone who wants to set up on him. The second reason for picking him was the massive damage output that psychic makes on anything which dosent resist it. Signal beam and focus blast make sure that hes going to remain unchallenged, even Tyranitar has to be careful about switching in to one of those moves.
Flygon: Choice Band
Adamant nature: 252Atk 80HP 176Spd
Earthquake
Outrage
Fire punch
U-Turn
Sweeper number two. Flygon I picked as it has a far better typing than Salamence which serves my team better, since its twin immunities means it can switch in on alot of moves without a care. And is immune to any paralasis thats not coming from a random body slam. U-Turn I have found extremely helpful, when the situation isnt to my favour out Flygon goes.
I picked Fire punch over blast/dragon claw/stone edge as I prefered to have more HP to take an attack when switching in, also Stone edge and Fire blasts's shakey accuracy put me off very quickly, and dragon claw I saw as not very useful as outrage is far stronger and I wont be staying in for very long with a choice item on anyway.
Empoleon: Pataya Berry
Modest nature: 252SpAtk 12HP 12SpDef 232Spd
Surf
Ice beam
Substitute
Agility
Final sweeper. Empoleon is for later sweeping when my opponent is running out of things that can stop it. Set up a substitute and agility, even without the berry activating Empoleons offense is very powerful, and with the berry (and torrent) its becomes brutal. The typing is also a reason I picked this pokemon, immunity to poison is very helpful.
I picked Ice beam over grass knot as I have little to none Ice moves on my team, and with a sub up Empoleon has little to fear from Salamence.
Dusknoir: Leftovers
Impish Nature: 252HP 252Def 6SpDef
Fire punch
Night Shade
Will-O-Wisp
Pain Split
Now onto the protection pokemon, Dusknoir helps keep stealth rocks up, although since Rotom-A does the job better I am thinking of switching to useing it, when I get platinum that is.
Will-O-Wisp is for the sweepers who try and set up on my pokemon, giving them something to worry about. Night shade I see as more useful than the other punchs since Dusknoirs attack is very poor with no investment.
Shaymin: Leftovers
Bold nature: 252HP 252Def 6SpAtk
Seed Flare
Aromatherapy
Rest
Leech Seed
My final pokemon, Shaymin I picked mainly because of its use of Aromatherapy and Seed Flare. The latter of which become extremely powerful when used in succesion meaning it can cause the opponent to switch or even get KOed if they dont expect much from this little pokemon.
Rest isa very obvious choice, fully healing the pokemon and all I have to do is switch out? Brilliant. Most people will just tell my to switch to useing a Celebi, but Shaymin is more useful to my team, as it lacks a weakness to Persuit (Which my Alakazam shares) and as my team switchs round alot I would prefer not to have that weakness preyed on.
There are a couple of pokemon here to keep the others alive or my opponents down.

Metagross: Leftovers
Adamant nature 252HP 236Atk 12Def 8Spd
Meteor Mash
Bullet Punch
Stealth Rock
Explosion
Ok so this is the lead and pokemon that started this team off. His main aim is to get the rocks up, damage as many pokemon as possible and then detonate and take someone with him. Explosion I find very useful for taking down a pokemon that is threatening my team and is being a right pain in the arse to take down. Meteor mash is over earthquake because I have yet to encounter a lead (me personally) that gets hurt more by earthquake than meteor mash, and the occasional attack rise is helpful.

Alakazam: Choice Specs
Synchronize
Timid Nature: 252SpAtk 252Spd 6HP
Psychic
Signal Beam
Focus Blast
Trick
My first sweeper, the ability to trick specs onto other pokemon was the main reason I picked Alakazam over other special sweepers, since he can cripple tanks/walls or anyone who wants to set up on him. The second reason for picking him was the massive damage output that psychic makes on anything which dosent resist it. Signal beam and focus blast make sure that hes going to remain unchallenged, even Tyranitar has to be careful about switching in to one of those moves.

Flygon: Choice Band
Adamant nature: 252Atk 80HP 176Spd
Earthquake
Outrage
Fire punch
U-Turn
Sweeper number two. Flygon I picked as it has a far better typing than Salamence which serves my team better, since its twin immunities means it can switch in on alot of moves without a care. And is immune to any paralasis thats not coming from a random body slam. U-Turn I have found extremely helpful, when the situation isnt to my favour out Flygon goes.
I picked Fire punch over blast/dragon claw/stone edge as I prefered to have more HP to take an attack when switching in, also Stone edge and Fire blasts's shakey accuracy put me off very quickly, and dragon claw I saw as not very useful as outrage is far stronger and I wont be staying in for very long with a choice item on anyway.

Empoleon: Pataya Berry
Modest nature: 252SpAtk 12HP 12SpDef 232Spd
Surf
Ice beam
Substitute
Agility
Final sweeper. Empoleon is for later sweeping when my opponent is running out of things that can stop it. Set up a substitute and agility, even without the berry activating Empoleons offense is very powerful, and with the berry (and torrent) its becomes brutal. The typing is also a reason I picked this pokemon, immunity to poison is very helpful.
I picked Ice beam over grass knot as I have little to none Ice moves on my team, and with a sub up Empoleon has little to fear from Salamence.

Dusknoir: Leftovers
Impish Nature: 252HP 252Def 6SpDef
Fire punch
Night Shade
Will-O-Wisp
Pain Split
Now onto the protection pokemon, Dusknoir helps keep stealth rocks up, although since Rotom-A does the job better I am thinking of switching to useing it, when I get platinum that is.
Will-O-Wisp is for the sweepers who try and set up on my pokemon, giving them something to worry about. Night shade I see as more useful than the other punchs since Dusknoirs attack is very poor with no investment.

Shaymin: Leftovers
Bold nature: 252HP 252Def 6SpAtk
Seed Flare
Aromatherapy
Rest
Leech Seed
My final pokemon, Shaymin I picked mainly because of its use of Aromatherapy and Seed Flare. The latter of which become extremely powerful when used in succesion meaning it can cause the opponent to switch or even get KOed if they dont expect much from this little pokemon.
Rest isa very obvious choice, fully healing the pokemon and all I have to do is switch out? Brilliant. Most people will just tell my to switch to useing a Celebi, but Shaymin is more useful to my team, as it lacks a weakness to Persuit (Which my Alakazam shares) and as my team switchs round alot I would prefer not to have that weakness preyed on.