I've been using this Sand team for a week or so now on PO, and it's pretty good, but I feel it could use some improvements.
The team
Tyranitar (M) @ Chople Berry
Trait: Sand Stream
EVs: 252 HP / 252 Atk / 4 Def
Brave Nature (+Atk, -Spd)
- Crunch
- Rock Slide
- Low Kick
- Protect
Without Tyranitar, this team could hardly be called a Sand team. Tyranitar is more often than not one of my leads. Max HP and Attack for bulk and power respectively, and a Brave nature with 0 Speed IVs so he has a better chance of outslowing (?) any opposing weather users and keep the weather up, as well as being able to perform under Trick Room. Crunch and Rock Slide are STAB attacks that can deal plenty of damage, and Low Kick is to hit things that resist Dark and Rock attacks, such as most Steel types and other Tyranitars. And Tyranitars last move is the VGC staple Protect, allowing Tyranitar to dodge an attack, and stall out Trick Room.
Terrakion @ Focus Sash
Trait: Justified
EVs: 4 HP / 252 Atk / 252 Spd
Adamant Nature (+Atk, -SAtk)
- Rock Slide
- Close Combat
- Quick Attack
- Protect
Terrakion is an absolute powerhouse in doubles. Max Attack and Speed in order to hit hard and fast. I've opted to use an Adamant nature over a Jolly nature as an Adamant Close Combat against 252/4 Tyranitar with a Chople Berry is guaranteed to OHKO, whereas Jolly Close Combat only has a 43.75% chance of OHKO'ing. Rock Slide is Terrakion's other STAB, doing plenty of damage to both opposing Pokemon. Quick Attack is to finish off any weakened opponents before they can attack, and Protect is staple. For the item, I went with Focus Sash over Rock/Fighting Gem or Life Orb because Terrakion is already a bit on the fragile side, and repeated use of Close Combat isn't helping. With Focus Sash, Terrakion is able to survive a hit after being knocked down to it's Sash, and can Protect the next turn to screw over the opponent hoping to clean up Terrakion, which is pretty fun to do.
Latios (M) @ White Herb
Trait: Levitate
EVs: 4 HP / 4 Def / 248 SAtk / 4 SDef / 248 Spd
Timid Nature (+Spd, -Atk)
- Draco Meteor
- Psychic
- Surf
- Protect
Latios is fast and powerful, and gives great offensive synergy to my team. Draco Meteor is the strongest attack in Latios arsenal, being able to KO or severely dent pretty much everything. Psychic is Latios' other STAB, hitting Fighting and Poison types for super effective damage. Surf rounds off Latios' attacks, hitting Fire, Rock, and Ground types. The EVs are what is listed on Smogon's page for Latios VGC 2012. I chose White Herb as Latios' item after seeing it used in a VGC 2012 final, and I really liked the idea of having the -2 SpA side-effect of Draco Meteor being removed without resorting to switching. The only problem with this set is that I have to be careful of Intimidate users such as Gyarados and Salamence causing my White Herb to be used up.
Zapdos @ Charti Berry
Trait: Pressure
EVs: 140 HP / 252 SAtk / 116 Spd
Modest Nature (+SAtk, -Atk)
- Thunderbolt
- Heat Wave
- Tailwind
- Detect
My second powerful special attacker, who also doubles as Tailwind support. I went with Thunderbolt over Discharge for Zapdos' main STAB as none of my team are immune to Electric moves, and more often than not I only need to hit one opposing Pokemon. Heat Wave is Zapdos' spread damage attack, and fills a much needed gap in offensive synergy within my team. Tailwind is to boost my teams speed so I can hit and potentially KO before the same happens to me. Detect is, as usual, to dodge incoming attacks, and was chosen over Protect in the rare case of Protect-Imprison users. Modest nature is used to boost Zapdos' SpA, as with Tailwind, there's isn't much need for a Speed boosting nature. The EVs used are Smogon's recommended set, and a Charti Berry is Zapdos' item to weaken the ever common Rock Slide.
Excadrill (F) @ Life Orb
Trait: Sand Rush
EVs: 4 HP / 252 Atk / 252 Spd
Adamant Nature (+Atk, -SAtk)
- Rock Slide
- X-Scissor
- Earthquake
- Protect
Excadrill was the main reason I went with a Sand team, as I never got to try out Sand Rush Excadrill in OU. Rock Slide and Earthquake are two powerful spread attacks. X-Scissor is to do massive damage to Cresselia and other bulky Psychic-types, and Protect is standard. Max Attack and Speed EVs so Excadrill can hit hard and fast, and an Adamant nature was chosen over Jolly due to Sand Rush boosting Excadrills Speed anyway. And lastly, a Life Orb so Excadrill gets extra power.
Heatran (F) @ Shuca Berry
Trait: Flash Fire
EVs: 4 HP / 252 SAtk / 252 Spd
Modest Nature (+SAtk, -Atk)
- Heat Wave
- Earth Power
- Hidden Power [Ice]
- Protect
Heatran is my main counter to Sun and Hail teams. Heat Wave is a powerful STAB coming off Heatrans already massive SpA. Earth Power and Hidden Power Ice give extra coverage, and hit Pokemon that can take Fire attacks relatively well, such as Chandelure and Salamence. And, as with every other Pokemon on my team, Protect is to dodge attacks and stall out Trick Room. Max SpA and Speed EVs let Heatran hit hard and fast, and a Modest nature lets Heatrans attacks do even more damage. Shuca Berry is to protect against the very common Earthquake, and other Ground-type attacks.
So that's my VGC 2012 Sand team. Looking at it, there are a few things I could change. Firstly, I don't actually use Excadrill all too often, and when I do, it only manages to hit once before being KO'd. Secondly, if I remove Excadrill, then Tyranitar is mostly useless, other than being able to counter opposing weather teams, so I could potentially replace Tyranitar with something else and turn the team into a general goodstuffs team.
The team

Tyranitar (M) @ Chople Berry
Trait: Sand Stream
EVs: 252 HP / 252 Atk / 4 Def
Brave Nature (+Atk, -Spd)
- Crunch
- Rock Slide
- Low Kick
- Protect
Without Tyranitar, this team could hardly be called a Sand team. Tyranitar is more often than not one of my leads. Max HP and Attack for bulk and power respectively, and a Brave nature with 0 Speed IVs so he has a better chance of outslowing (?) any opposing weather users and keep the weather up, as well as being able to perform under Trick Room. Crunch and Rock Slide are STAB attacks that can deal plenty of damage, and Low Kick is to hit things that resist Dark and Rock attacks, such as most Steel types and other Tyranitars. And Tyranitars last move is the VGC staple Protect, allowing Tyranitar to dodge an attack, and stall out Trick Room.

Terrakion @ Focus Sash
Trait: Justified
EVs: 4 HP / 252 Atk / 252 Spd
Adamant Nature (+Atk, -SAtk)
- Rock Slide
- Close Combat
- Quick Attack
- Protect
Terrakion is an absolute powerhouse in doubles. Max Attack and Speed in order to hit hard and fast. I've opted to use an Adamant nature over a Jolly nature as an Adamant Close Combat against 252/4 Tyranitar with a Chople Berry is guaranteed to OHKO, whereas Jolly Close Combat only has a 43.75% chance of OHKO'ing. Rock Slide is Terrakion's other STAB, doing plenty of damage to both opposing Pokemon. Quick Attack is to finish off any weakened opponents before they can attack, and Protect is staple. For the item, I went with Focus Sash over Rock/Fighting Gem or Life Orb because Terrakion is already a bit on the fragile side, and repeated use of Close Combat isn't helping. With Focus Sash, Terrakion is able to survive a hit after being knocked down to it's Sash, and can Protect the next turn to screw over the opponent hoping to clean up Terrakion, which is pretty fun to do.

Latios (M) @ White Herb
Trait: Levitate
EVs: 4 HP / 4 Def / 248 SAtk / 4 SDef / 248 Spd
Timid Nature (+Spd, -Atk)
- Draco Meteor
- Psychic
- Surf
- Protect
Latios is fast and powerful, and gives great offensive synergy to my team. Draco Meteor is the strongest attack in Latios arsenal, being able to KO or severely dent pretty much everything. Psychic is Latios' other STAB, hitting Fighting and Poison types for super effective damage. Surf rounds off Latios' attacks, hitting Fire, Rock, and Ground types. The EVs are what is listed on Smogon's page for Latios VGC 2012. I chose White Herb as Latios' item after seeing it used in a VGC 2012 final, and I really liked the idea of having the -2 SpA side-effect of Draco Meteor being removed without resorting to switching. The only problem with this set is that I have to be careful of Intimidate users such as Gyarados and Salamence causing my White Herb to be used up.

Zapdos @ Charti Berry
Trait: Pressure
EVs: 140 HP / 252 SAtk / 116 Spd
Modest Nature (+SAtk, -Atk)
- Thunderbolt
- Heat Wave
- Tailwind
- Detect
My second powerful special attacker, who also doubles as Tailwind support. I went with Thunderbolt over Discharge for Zapdos' main STAB as none of my team are immune to Electric moves, and more often than not I only need to hit one opposing Pokemon. Heat Wave is Zapdos' spread damage attack, and fills a much needed gap in offensive synergy within my team. Tailwind is to boost my teams speed so I can hit and potentially KO before the same happens to me. Detect is, as usual, to dodge incoming attacks, and was chosen over Protect in the rare case of Protect-Imprison users. Modest nature is used to boost Zapdos' SpA, as with Tailwind, there's isn't much need for a Speed boosting nature. The EVs used are Smogon's recommended set, and a Charti Berry is Zapdos' item to weaken the ever common Rock Slide.

Excadrill (F) @ Life Orb
Trait: Sand Rush
EVs: 4 HP / 252 Atk / 252 Spd
Adamant Nature (+Atk, -SAtk)
- Rock Slide
- X-Scissor
- Earthquake
- Protect
Excadrill was the main reason I went with a Sand team, as I never got to try out Sand Rush Excadrill in OU. Rock Slide and Earthquake are two powerful spread attacks. X-Scissor is to do massive damage to Cresselia and other bulky Psychic-types, and Protect is standard. Max Attack and Speed EVs so Excadrill can hit hard and fast, and an Adamant nature was chosen over Jolly due to Sand Rush boosting Excadrills Speed anyway. And lastly, a Life Orb so Excadrill gets extra power.

Heatran (F) @ Shuca Berry
Trait: Flash Fire
EVs: 4 HP / 252 SAtk / 252 Spd
Modest Nature (+SAtk, -Atk)
- Heat Wave
- Earth Power
- Hidden Power [Ice]
- Protect
Heatran is my main counter to Sun and Hail teams. Heat Wave is a powerful STAB coming off Heatrans already massive SpA. Earth Power and Hidden Power Ice give extra coverage, and hit Pokemon that can take Fire attacks relatively well, such as Chandelure and Salamence. And, as with every other Pokemon on my team, Protect is to dodge attacks and stall out Trick Room. Max SpA and Speed EVs let Heatran hit hard and fast, and a Modest nature lets Heatrans attacks do even more damage. Shuca Berry is to protect against the very common Earthquake, and other Ground-type attacks.
So that's my VGC 2012 Sand team. Looking at it, there are a few things I could change. Firstly, I don't actually use Excadrill all too often, and when I do, it only manages to hit once before being KO'd. Secondly, if I remove Excadrill, then Tyranitar is mostly useless, other than being able to counter opposing weather teams, so I could potentially replace Tyranitar with something else and turn the team into a general goodstuffs team.