This has mostly been dead so I am going to revive it.
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Darkrai
Type: Dark
Base Stats: 70 HP/90 Atk/90 Def/135 SpA/90 SpD/125 Spe
Ability: Bad Dreams
A fearsome sweeper that can utilize Dark Void, a 80% accurate Sleep inducing move, to send even would-be counters a-snoozing, giving it ample time to make use of Nasty Plot to set up for a deadly sweep. Darkrai's superb Special Attack stat is nicely complemented by a large array of powerful attacks, including Dark Pulse, Thunder, Spacial Rend, Focus Blast, and Ice Beam. Darkrai can also surprise opponents with Swords Dance boosted Sucker Punches, Focus Punches, and Brick Breaks coming off of its decent Attack stat.
Deoxys-A
Type: Psychic
Base Stats: 50 HP/180 Atk/20 Def/180 SpA/20 SpD/150 Spe
Ability: Pressure
This Psychic-type Pokemon, despite having absolutely pitiful defensive stats, boasts the highest offensive stats of any Pokemon, and with access to moves such as Ice Beam, Shadow Ball, Thunder, Grass Knot, Superpower, ExtremeSpeed, Signal Beam, and the elemental punches Deoxys-A is capable of 2HKOing anything in the game at worst. Deoxys-A can also perform well as a suicide lead to get up Stealth Rock and/or Spikes quickly and efficiently, and it can also surprise enemy attackers with Counter or Mirror Coat.
Deoxys-D
Type: Psychic
Base Stats: 50 HP/70 Atk/160 Def/70 SpA/160 SpD/90 Spe
Ability: Pressure
The defensive counterpart of Deoxys-A. Despite having low HP, Deoxys-D's amazing Defense and Special Defense stats combined with reliable healing in Recover makes it an excellent general purpose tank as well as a counter to several top threats, such as Dragon Dance and Swords Dance Rayquaza as well as Mixed Dialga. Deoxys-D can use its defenses to shrug off hits while laying down Stealth Rock or Spikes, spreading around status with Toxic or Thunder Wave, or by using Seismic Toss and/or Night Shade to deal reliable damage to opponents while bypassing Deoxys-D's low offensive stats. Deoxys-D can also use Calm Mind to potentially cause a bit of damage to the opponent's team, with access to Ice Beam, Shadow Ball, Thunder, Grass Knot, and Signal Beam to give it wide type coverage to help make up for its low offensive stats. Deoxys-D can also use Taunt to stop set-up sweepers as well as Forretress and Wobbuffet, both of whom may try to set-up on it.
Deoxys-S
Type: Psychic
Base Stats: 50 HP/95 Atk/90 Def/95 SpA/90 SpD/180 Spe
Ability: Pressure
The fastest Pokemon in the game, Deoxys-S makes for a fantastic suicide lead. With access to both Stealth Rock and Spikes, it can use its tremendous Speed stat to possibly lay down multiple layers of entry hazards before going down. Deoxys-S also has the fastest Taunt in the game, which can easily shut down enemy supporters or set-up sweepers. If one should wish, Deoxys-S can use its great movepool (Identical to Deoxys-A's movepool) to function as an excellent revenge killer and late game cleaner.
Dialga
Type: Steel / Dragon
Base Stats: 100 HP/120 Atk/120 Def/150 SpA/100 SpD/90 Spe
Ability: Pressure
Dialga is one of the most threatening offensive forces in Ubers, as both of its attacking stats are very high and it has an extremely wide movepool to complement it. Dialga is most commonly seen as a special attacker backed by Life Orb, Choice Specs, or Choice Scarf, with its special movepool including Dragon Pulse, Draco Meteor, Fire Blast, Thunder, Earth Power, Aura Sphere, and Flash Cannon. Dialga also has access to physical moves such as Outrage, Earthquake, Shadow Claw, Dragon Claw, and Brick Break, allowing it to become a very threatening mixed attacker, or even a pure physical attacker when Bulk Up or a Choice Band is also in use. Dialga is no slouch defensively either. Its very good defensive stats combined with arguably the best defensive type combination in the game as well as access to supporting moves such as Stealth Rock, Thunder Wave, and Toxic allows Dialga to become an excellent supporting tank, despite Rest being its only form of recovery.
Garchomp
Type: Dragon / Ground
Base Stats: 108 HP/130 Atk/95 Def/80 SpA/85 SpD/102 Spe
Ability: Sand Veil
Garchomp has one of the best offensive type combinations in the game. The coverage provided by Garchomp's dual STABs is easily taken advantage of thanks to its high Attack and Speed stats. Swords Dance makes Garchomp into an extremely potent sweeper, with powerful attacks such as Dragon Claw, Outrage, Earthquake, Fire Fang, Stone Edge, Crunch, and Aqua Tail offering tons of power and great type coverage. Garchomp can also take advantage of a Choice Band to hit hard without needed set-up or a Choice Scarf to become a fast, deadly revenge killer.
Giratina
Type: Ghost / Dragon
Base Stats: 150 HP/100 Atk/120 Def/100 SpA/120 SpD/90 Spe
Ability: Pressure
Giratina's colossal defenses allow it to serve as a great wall and spinblocker. Despite Giratina's defenses being equal, it is generally seen as a physical wall thanks to access to Will-o-Wisp, allowing it to cripple the majority of physical attackers in Ubers. Most of Giratina's weaknesses also tend to come from special attacks, thus meaning that Giratina would struggle to wall the powerful special attacks of Ubers. Giratina can also hit hard with its decent offenses and STAB Dragon Claw, Dragon Pulse, Outrage, Shadow Claw, and/or Shadow Ball, and can even use Calm Mind to become a threatening set-up presence. Giratina can also surprise opponents with a Choice Band or Choice Specs set to hit hard with attacks such as Thunder, Earthquake, Shadow Force, Earth Power, Aura Sphere, and Stone Edge in addition to the other STAB moves mentioned previously.
Giratina-O
Type: Ghost / Dragon
Base Stats: 150 HP/120 Atk/100 Def/120 SpA/100 SpD/90 Spe
Ability: Pressure
Giratina's more offensive cousin, and perhaps the best offensive spinblocker in the game, Giratina-O boasts powerful Ghost- and Dragon-type STAB, which together hit a large portion of the Ubers tier for super effective damage. Three immunities, immunity to Trick and Knock Off, and incredible bulk allow Giratina-O to switch in rather easily, despite having weaknesses to some of the most common attack types in Ubers, with those types being Dragon, Ice, Ghost, and Dark. Giratina-O can make use of Calm Mind along with Dragon Pulse, Shadow Ball, Aura Sphere, Thunder, and Earth Power to hit very hard on special side, as well as Dragon Claw, Shadow Claw, Shadow Force, Stone Edge, and Earthquake to smash things of the physical end of the spectrum. High power attacks such as Draco Meteor and Outrage, combined with great attacking stats, also allow Giratina-O to be a powerful mixed attacker. In addition, Giratina-O is one of the few Ubers that gets a priority move: Shadow Sneak. With this move, Giratina-O can serve as a great check to Latias, Latios, Mewtwo, and Deoxys.
Groudon
Type: Ground
Base Stats: 100 HP/150 Atk/140 Def/100 SpA/90 SpD/90 Spe
Ability: Drought
Groudon's extremely good Attack and good defenses allow it to be one of the most threatening physical attackers in Ubers. Groudon learns powerful attacks such as Earthquake, Dragon Claw, Stone Edge, and Fire Punch that offer good type coverage as well, and when combined with a Choice Band, Swords Dance to boost Attack even more, or Rock Polish to make up for Groudon's below average Speed stat, the Continent Pokemon will certainly be very hard to stop. Groudon is also a popular recipient for Uber Baton Pass teams thanks to its sky-high Attack stat and its excellent type coverage. Groudon is also a very capable physical wall, making an excellent answer to threats such as Metagross, Garchomp, Rayquaza, Lucario, and most other physical sweepers thanks to its high Defense stat. Access to Toxic, Thunder Wave, Stealth Rock, and even Lave Plume to potentially spread burns allow Groudon to be an excellent supporter as well. Thanks to is ability, Drought, Groudon brings everlasting sunlight to the battle. This makes Groudon the bane of Rain teams as well as a massive boon to Ubers Sunny Day teams. Pokemon such as Heatran, Ho-Oh, Jumpluff, and Shiftry all become massive threats thanks to Groudon's sunlight.
Ho-Oh
Type: Fire / Flying
Base Stats: 106 HP/130 Atk/90 Def/110 SpA/154 SpD/90 Spe
Ability: Pressure
Ho-Oh's STAB attacks, Sacred Fire and Brave Bird, alone make it nearly impossible to wall, and when combined with other attacks such as Earthquake and Punishment, switching in anything will be a daunting prospect. That, combined with Ho-Oh's awesome Special Defense stat and Recover or Roost for reliable recovery, it can be very tough to take down if Stealth Rock is not up on Ho-Oh's side of the field. Ho-Oh, should you choose, can also try its hand at special attacking with Calm Mind, Fire Blast, Thunder, and Shadow Ball.
Kyogre
Type: Water
Base Stats: 100 HP/100 Atk/90 Def/150 SpA/140 SpD/90 Spe
Ability: Drizzle
The #1 used Pokemon in Ubers, and for good reason. Kyogre's fantastic Special Attack stat, combined with rain-fueled Water STAB (thanks to Drizzle) along with Ice Beam and Thunder for nearly unresisted coverage makes Kyogre incredibly hard to switch into. Kyogre can use Calm Mind to boost the power of its attacks even more, Choice Scarf to make up for its below average Speed stat, or Choice Specs to turn it into an instant offensive juggernaut. Choice Scarf and Choice Specs also allows Kyogre to abuse Water Spout, which reaches a jaw-dropping 337.5 base power when Kyogre is at 100% HP, factoring in STAB and the rain. Kyogre is also very strong defensively, as it can wall some of the top threats of Ubers such as Mewtwo, Darkrai, Groudon, some Rayquaza, some Garchomp, and some Ho-Oh when defensively EVed. Toxic and Thunder Wave also allows Kyogre to mess up many of its common counters, such as Latias and Palkia. The rain Kyogre provides, courtesy of Drizzle, allow fuels many dangerous threats such as Kingdra, Palkia, and Manaphy.
Latias
Type: Dragon / Psychic
Base Stats: 80 HP/80 Atk/90 Def/110 SpA/130 SpD/110 Spe
Ability: Levitate
Latias' success in Ubers is attributed to its special hold item: Soul Dew. This item boosts Latias' Special Attack and Special Defense stats to extremely high levels, allowing it to be a powerful sweeper with Calm Mind and STAB Dragon Pulse, Grass Knot, and Thunder. Latias also gets Wish, Toxic, Thunder Wave, Dual Screens, and Safeguard as support options, and when combined with reliable healing in Recover, Latias can be a sturdy special tank as well. Refresh in tandem with Calm Mind and Recover also allows Latias to get past some special walls, such as Blissey.
Latios
Type: Dragon / Psychic
Base Stats: 80 HP/90 Atk/80 Def/130 SpA/110 SpD/110 Spe
Ability: Levitate
Latios also gets to use Soul Dew, and he is essentially a frailer but stronger version of Latias. He gets many of the same attacks as Latias (although Latios usually uses Draco Meteor more than Latias), but Latios receives Memento and Dragon Dance in lieu of Wish. Dragon Dance allows Latios to use a mixed or physical set to surprise opponents, or simply for a Speed boost to outrun common Choice Scarf users. Memento gives Latios an advantage over Latias when using Dual Screens, as with it Latios can sacrifice itself to let a deadly sweeper come in for free and start to rampage through the opponent's team.
Lugia
Type: Psychic / Flying
Base Stats: 106 HP/90 Atk/130 Def/90 SpA/154 SpD/110 Spe
Ability: Pressure
Lugia is one of the sturdiest walls in the game, boasting incredible defensive stats as well as a wide supporting movepool. Lugia can easily wall things such as Groudon, Garchomp, Rayquaza, Metagross, and special attackers such as Dialga, Palkia, and some Giratina-O with ease while spreading around status in the form of Toxic and Thunder Wave. Lugia can also use Reflect and Light Screen to boost its impressive defenses even more, Whirlwind to shuffle the opponents team around while possibly spreading damage for entry hazards, and Recover or Roost to reliably heal itself. Lugia can also surprise opponents with Calm Mind along with attacks such as Ice Beam, Thunder, Earth Power, Aeroblast, and Dragon Pulse, turning it into an offensive threat. Lugia also gets Trick, allowing it to potentially cripple one of its counters by Tricking a Choice item onto the counter.
Manaphy
Type: Water
Base Stats: 100 HP/100 Atk/100 Def/100 SpA/100 SpD/100 Spe
Ability: Hydration
While Manaphy at first may seem to be outclassed by Kyogre and Palkia, Manaphy has a few advantages that should not be overlooked. Tail Glow allows Manaphy to set-up faster than both Kyogre and Palkia, and when combined with powerful attacks such as Surf, Ice Beam, Grass Knot, and Energy Ball, Manaphy can beat a strong offensive threat. Manaphy's ability, Hydration, allows it to shrug off status in the rain as well, meaning that it can use Rest to restore all of its HP and then wake up instantly thanks to Hydration, provided it is raining. Manaphy also has some interesting support options available to it, such as Toxic, Dual Screens, and U-turn for scouting the opponent's team. Manaphy isn't seen much, but it's not to be underestimated.
Mew
Type: Psychic
Base Stats: 100 HP/100 Atk/100 Def/100 SpA/100 SpD/100 Spe
Ability: Synchronize
Mew is one of the most versatile Pokemon in the game, but it is most commonly seen as a Baton Passer. The reason for this is that Mew can Baton Pass +2 of any stat, it gets Taunt to stop phasing attempts, and it can take a few its with s good defenses while setting up. All of this makes Mew the most threatening Baton Passer in the game, and a successful pass by Mew could make or break a game. In addition, Mew is an excellent supporter with access to Trick Room, Toxic, Thunder Wave, Will-o-Wisp, Hypnosis, Dual Screens, Stealth Rock, and U-turn for scouting purposes. Mew can also use its excellent offensive movepool, including Fire Blast, Thunder, Blizzard, Dark Pulse, Earthquake, Shadow Claw, Explosion, and much more in conjunction with Rock Polish, Swords Dance, and/or Nasty Plot to possibly sweep an enemy team, but generally Mew is outclassed as a sweeper by Mewtwo.
Mewtwo
Type: Psychic
Base Stats: 106 HP/110 Atk/90 Def/154 SpA/90 SpD/130 Spe
Ability: Pressure
Mewtwo main strength is in its versatility, as it excels as being a sweeper, supporter, and a wall. Mewtwo's prodigious Special Attack and Speed coupled with a wide array of attacks such as Calm Mind, Aura Sphere, Fire Blast, Thunder, Ice Beam, Shadow Ball, Grass Knot, and many more make Mewtwo a very frightening special sweeper. It can also take advantage of items such as Life Orb, Choice Specs, and Choice Scarf to boost its sweeping potential even more. Selfdestruct and Focus Punch let Mewtwo get around special walls as well, and its good Attack coupled with Bulk Up, Ice Punch, Brick Break, Earthquake, and Fire Punch let it sweep on the physical side too. Mewtwo can also be an excellent supporter with options such as Taunt, Recover, Reflect, Light Screen, Toxic, Will-O-Wisp, and Trick.
Palkia
Type: Water / Dragon
Base Stats: 90 HP/120 Atk/100 Def/150 SpA/120 SpD/100 Spe
Ability: Pressure
Palkia is known for having very good offense stats as well as being one of the few Pokemon not 2HKOed by a Water Spout from a Choice Specs Kyogre. Palkia's incredible Special Attack lets it use its special movepool, which includes Dragon Pulse, Spacial Rend, Draco Meteor, Fire Blast, Thunder, Earth Power, Aura Sphere, Surf, and Hydro Pump, to wrek havoc on its foes when using a Lustrous Orb, Choice Specs, or Choice Scarf. Palkia, like Dialga, also has access to physical moves such as Outrage, Aqua Tail, Earthquake, Shadow Claw, Dragon Claw, and Focus Punch, allowing it to become a very threatening physical or mixed sweeper.
Rayquaza
Type: Dragon / Flying
Base Stats: 105 HP/150 Atk/90 Def/150 SpA/90 SpD/95 Spe
Ability: Air Lock
Rayquaza is one of the most powerful offensive threats in Ubers. It boasts incredibly high offenses on both Attack and Special Attack, and these high stats will wreak utter devastation on an opponent's team when combined with high powered moves such as Draco Meteor, Outrage, Fire Blast, Overheat, Earthquake, ExtremeSpeed, and Brick Break. Rayquaza can also make use of Swords Dance and Dragon Dance alongside Life Orb to become an offensive juggernaut in just one turn, or it can just use Choice Band or Choice Specs to hit hard without having to set up. Air Lock, Rayquaza's unique ability, also makes it a very threatening presence to weather teams by nullifying the effects of rain, sunlight, and sandstorm.
Shaymin-S
Type: Grass / Flying
Base Stats: 100 HP/103 Atk/75 Def/120 SpA/75 SpD/127 Spe
Ability: Serene Grace
Shaymin-S is well known for its Serene Grace ability, which boosts Air Slash to a 60% flinch rate and Seed Flare's chance of lowering the opponent's Special Defense by two stages to 80%. When combined with offensive coverage moves such as Earth Power, Hidden Power Fire, or Hidden Power Ice, Shaymin-S can be a menacing offensive threat with or without Choice Specs, Choice Scarf, or Life Orb. In addition, Shaymin-S is also the fastest user of the Substitute and Leech Seed combo, allowing it to stall out many Pokemon while keeping itself at optimal health.
Wobbuffet
Type: Psychic
Base Stats: 190 HP/33 Atk/58 Def/33 SpA/58 SpD/33 Spe
Ability: Shadow Tag
Although Wobbuffet's stats are bad in everything sans HP and it learns a grand total of 8 moves, it is much more threatening then it looks. Wobbuffet's unique ability, Shadow Tag, allows it to trap any Pokemon in the battle except another Wobbuffet. When combined with Counter, Mirror Coat, and Encore, Wobbuffet will all but ensure death on at least one of your opponent's Pokemon. Safeguard combined with the aforementioned Encore also allows deadly sweepers on Wobbuffet's team to come in and set up free of status and/or a super effective counter attack. Tickle, although rare, allows Wobbuffet to devastate enemy walls when paired with a strong user of Pursuit.
