This is my first attempt at a team
EDIT
Tyranitar @ Chesto Berry
252 HP / 32 Atk / 224 SpD
Adamant
31 HP / 31 Attack / 31 Speed
~ Stone Edge
~ Pursuit
~ Earthquake
~ Stealth Rock
I chose Tyranitar to serve as my lead because I like his ability and his attack stat is better than Hippowdon's. His main purpose is to summon a sandstorm and shut down other common leads by breaking their focus sashes with Sandstorm. Late-game he will serve as a Special wall and is a good counter to ghost and psychic sweepers.
I'll have to switch Tyranitar out if he is facing any of his 6 weaknesses.
Scizor @ Life Orb
252 At / 252 Spe / 4 HP
Adamant
31 Attack / 31 Speed
~ Swords Dance
~ Bullet Punch
~ Superpower
~ Bug Bite
I chose Scizor for this team because of his typing and priority move Bullet Punch. Scizor is meant as a late game sweeper, but I have found him reliable as team support with weakening my foes. If threats (Fire type) have been removed then I'll fire off a Swords Dance and Bullet Punch everything to death.
If a fire type switches in, I'll switch to Starmie.
Starmie @ Leftovers
136 HP / 156 Def / 216 Spe
Timid
~ Rapid Spin
~ Surf
~ Thunderbolt
~ Recover
I chose Starmie to be my main team support because of the Natural Cure ability, which is great for getting rid of toxic spikes. Starmie can heal status ailments and HP and counter the types that are super effective against my teammates. Thunderbolt is for other water types and Skarmory. Starmie can also serve as my physical wall and can be very powerful if the foe doesn't resist its attacks.
Heatran @ Choice Scarf
4 Atk / 252 SpA / 252 Spe
Naive
~ Fire Blast
~ Earth Power
~ Hidden Power Electric
~ Dragon Pulse
Heatran is Scizor's partner and will switch into all fire types and kill them off with Earth Power. Hidden Power Electric for super effective water types, Fire Blast for STAB. I need a replacement for Dragon Pulse, perhaps Magna Storm.
Metagross @ Leftovers
252 HP / 244 Def / 12 Spe
Adamant
~ Light Screen
~ Meteor Mash
~ Earthquake
~ ThunderPunch
Metagross is here as a tank as a powerful physical attacker. He provides great type resistances, and massive attack and defenses. The set is on par with his good type-coverage, and Light Screen is there for SpD coverage. I'm considering replacing something with Bullet Punch. ThunderPunch is necessary for Water types and Skarmory but for pretty much everything else I'll use STAB Meteor Mash.
Mamoswine @ Choice Band
252 Atk / 4 Def / 252 Spe
Jolly
31 HP / 31 Attack / 31 Speed
~ Earthquake
~ Ice Shard
~ Stone Edge
~ Superpower
I chose to add Mamoswine to the team because of his high base attack stat, priority moves, and good variety. He'll be used as a backup physical attacker and is good for countering electric types that switch into Starmie. Earthquake will be my primary attack for super-effective and neutral damage, and the others are there for super effective/priority damage. I'll save for second-to-last if I can, but he'll go out earlier if he needs to counter an electric type.
EDIT

Tyranitar @ Chesto Berry
252 HP / 32 Atk / 224 SpD
Adamant
31 HP / 31 Attack / 31 Speed
~ Stone Edge
~ Pursuit
~ Earthquake
~ Stealth Rock
I chose Tyranitar to serve as my lead because I like his ability and his attack stat is better than Hippowdon's. His main purpose is to summon a sandstorm and shut down other common leads by breaking their focus sashes with Sandstorm. Late-game he will serve as a Special wall and is a good counter to ghost and psychic sweepers.
I'll have to switch Tyranitar out if he is facing any of his 6 weaknesses.

Scizor @ Life Orb
252 At / 252 Spe / 4 HP
Adamant
31 Attack / 31 Speed
~ Swords Dance
~ Bullet Punch
~ Superpower
~ Bug Bite
I chose Scizor for this team because of his typing and priority move Bullet Punch. Scizor is meant as a late game sweeper, but I have found him reliable as team support with weakening my foes. If threats (Fire type) have been removed then I'll fire off a Swords Dance and Bullet Punch everything to death.
If a fire type switches in, I'll switch to Starmie.

Starmie @ Leftovers
136 HP / 156 Def / 216 Spe
Timid
~ Rapid Spin
~ Surf
~ Thunderbolt
~ Recover
I chose Starmie to be my main team support because of the Natural Cure ability, which is great for getting rid of toxic spikes. Starmie can heal status ailments and HP and counter the types that are super effective against my teammates. Thunderbolt is for other water types and Skarmory. Starmie can also serve as my physical wall and can be very powerful if the foe doesn't resist its attacks.

Heatran @ Choice Scarf
4 Atk / 252 SpA / 252 Spe
Naive
~ Fire Blast
~ Earth Power
~ Hidden Power Electric
~ Dragon Pulse
Heatran is Scizor's partner and will switch into all fire types and kill them off with Earth Power. Hidden Power Electric for super effective water types, Fire Blast for STAB. I need a replacement for Dragon Pulse, perhaps Magna Storm.

Metagross @ Leftovers
252 HP / 244 Def / 12 Spe
Adamant
~ Light Screen
~ Meteor Mash
~ Earthquake
~ ThunderPunch
Metagross is here as a tank as a powerful physical attacker. He provides great type resistances, and massive attack and defenses. The set is on par with his good type-coverage, and Light Screen is there for SpD coverage. I'm considering replacing something with Bullet Punch. ThunderPunch is necessary for Water types and Skarmory but for pretty much everything else I'll use STAB Meteor Mash.

Mamoswine @ Choice Band
252 Atk / 4 Def / 252 Spe
Jolly
31 HP / 31 Attack / 31 Speed
~ Earthquake
~ Ice Shard
~ Stone Edge
~ Superpower
I chose to add Mamoswine to the team because of his high base attack stat, priority moves, and good variety. He'll be used as a backup physical attacker and is good for countering electric types that switch into Starmie. Earthquake will be my primary attack for super-effective and neutral damage, and the others are there for super effective/priority damage. I'll save for second-to-last if I can, but he'll go out earlier if he needs to counter an electric type.