Defensive:
Blissey
Type: Normal
Base Stats: 255 HP / 10 Atk / 10 Def / 75 SpA / 135 SpD / 55 Spe
Abilities: Natural Cure / Serene Grace / Healer (Unreleased)
Despite receiving no new toys from BW, and in fact facing greater competition thanks to the huge buff to Chansey, the (original) pink blob proves frustratingly resilient. With a near-unmatched ability to wall just about any special attacker in the game, Blissey can find a place in any team hurting for a bit more special bulk. With a wide array of support moves, including Toxic, Thunder Wave, Heal Bell, and the newly buffed Wish that allows her to fully revitalize almost all Pokemon in the game, Blissey can be a fantastic team supporter, cleric, or status-spreader on stall and offensive teams alike. Despite being somewhat outclassed in defensively by Eviolite Chansey, Blissey maintains some advantages of its own that account for its greater usage. First, her usable base 75 Special Attack stat means that Blissey can run Ice Beam or Flamethrower to take advantage of her surprising physical bulk—largely due to her fantastic HP stat— (remove em dash); secondly, Leftovers negates residual damage Blissey may take from weather, and also helps offset whatever more damage she would take than Chansey. With massive Special Defense, decent physical Defense, a usable Special Attack and a good movepool, Blissey yet again proves that if something isn't broken, you need not fix it.
Bronzong
Type: Steel / Psychic
Base Stats: 67 HP / 89 Atk / 116 Def / 79 SpA / 116 SpD / 33 Spe
Abilities: Levitate / Heatproof / Heavy Metal (Unreleased)
With fantastic mixed defenses, and a combination of typing and choice of abilities that gives it only one weakness, Bronzong is a fantastic mixed wall that can take on a multitude of threats without breaking a sweat. Thanks to its Steel typing, Bronzong is one of the few reliable checks to the ferocious Dragon-types that roam OU, including Latios and Haxorus. Bronzong functions brilliantly in a support role, as it can reliably set up Stealth Rock, as well as provide dual screens and Trick Room support. Bronzong also has the ability to go on the offense as a tank that can both take hits and deal damage; such a set commonly sports Earthquake, Gyro Ball, and Hidden Power Ice to take on as many different Pokemon as possible. However, (comma) Bronzong isn't completely invulnerable. Its low HP stat and lack of reliable recovery means that it will easily be whittled down over the course of the match. All in all, Bronzong is a competent Pokemon that when used rightly, will be a very effective use of a teamslot.
Chansey
Type: Normal
Base Stats: 250 HP / 5 Atk / 5 Def / 35 SpA / 105 SpD / 50 Spe
Abilities: Natural Cure / Serene Grace / Healer (Unreleased)
In previous generations, Chansey found itself overshadowed by its evolution, Blissey, who had better stats both offensively and defensively. However, with the advent of BW came a new item, the Eviolite, which increases the defenses of NFE Pokemon by 50%. This instantly transformed Chansey into an enormously bulky Pokemon, who can wall a huge number of threats with defenses that now far surpass Blissey's, as well as reliable recovery in the form of Softboiled. BW also brought about a change in the mechanics of the move Wish; Chansey can now pass enormous 352 HP Wishes to its teammates. It can thus contribute to its team in many ways: aside from Wish, it gets access to status moves such as Toxic and Thunder Wave, as well as Aromatherapy and Heal Bell. It can alternatively be a pure wall that focuses on walling threats and forcing switches with its huge defensive stats, chipping away at the opponent's health mainly through residual damage. However, Chansey remains completely outclassed by Blissey when it comes to offense. Despite having a fantastic special movepool, Chansey cannot put it to good use with its deplorable base 35 Special Attack and thus has to resort to Seismic Toss; this leaves Chansey without any form of direct offense against Ghost-types. Having to hold Eviolite also deprives Chansey of Leftovers recovery, a disadvantage particularly in unfavorable weather. Despite these flaws, Chansey shines as one of the best special walls in the metagame and is one defensive threat which every team should be prepared for.
Deoxys-D
Type: Psychic
Base Stats: 50 HP / 70 Atk / 160 Def / 70 SpA / 160 SpD / 90 Spe
Ability: Pressure
With enormous equal base 160 defenses, a gigantic support movepool that includes a reliable recovery move, and the ability Pressure, Deoxys-D appears tailor-made for defensive playstyles. Access to Cosmic Power and Recover, as well as a wide variety of support moves such as Toxic, Taunt, Magic Coat, and Protect, Deoxys-D can stall out a large number of threats. It is hardly limited to stalling, though: it can utilize its fantastic defensive stats to lay entry hazards such as Spikes, or support a frail sweeper by setting up Reflect and Light Screen. However, Deoxys-D's stalling capabilities are undermined by its poor base 50 HP stat and a weakness to Pursuit courtesy of its Psychic typing, which also gives Deoxys-D weaknesses to common Ghost- and Dark-type attacks. This means that Pokemon such as Chandelure and Hydreigon can easily break through Deocys-D's defenses with their powerful STAB attacks. Deoxys-D is also prone to being Taunt bait for the likes of Sableye and Mew, unless it carries Magic Coat. Despite these flaws, Deoxys-D stands out as one of the most potent stallers in the metagame that can stall out entire unprepared teams.
Dragonite
Type: Dragon / Flying
Base Stats: 91 HP / 134 Atk / 95 Def / 100 SpA / 100 SpD / 80 Spe
Abilities: Inner Focus / Multiscale
Despite Dragonite's excellent natural bulk, it has usually been outclassed in one way or another in attempts to run defensive sets. Multiscale changed everything for Dragonite, making bulky Dragon Dance sets much harder to take down and creating new sets. In early BW, a set of Thunder Wave / Substitute / Roost / Dragon Tail began to catch on, its ability to paralyze hard hitters and wait for a full paralysis with Substitute and Roost made it a very tough wall to overcome and a very useful phazer. A Fire-type attack over Thunder Wave also catches a lot of normal counters, such as Skarmory, Forretress, and Tangrowth, off guard. Dragon Dance over Thunder Wave and Dragon Claw over Dragon Tail has become a bulky set-up sweeper famous for cleaning defensive teams as the last Pokemon. Lastly, Dragonite can run defensive sets in the rain with Hurricane posing a huge threat to Pokemon like Celebi and Virizion, which naturally trouble rain teams. Whether relentlessly setting up with Dragon Dance or phazing endlessly with Dragon Tail, Dragonite can be one of the greatest annoyances defensively if you don't prepare for it.
Ferrothorn
Type: Grass / Steel
Base Stats: 74 HP / 94 Atk / 131 Def / 54 SpA / 116 SpD / 20 Spe
Ability: Iron Barbs
With 74 / 131 / 116 defenses and a typing which gives it useful resistances to common Dragon-, Water-, Ice-, and Electric-type attacks, it is little wonder that Ferrothorn is one of the best walls in the game. In a metagame dominated by weather, Ferrothorn is an extremely useful check to rain-based teams, easily absorbing powerful attacks from the likes of Rotom-W, Starmie, and Kingdra. Ferrothorn's unique ability, Iron Barbs, also adds greatly to the headaches of physically based Pokemon and Rapid Spinners, and is an especially great way to pick off weakened Pokemon by just switching in. Ferrothorn's movepool is equally impressive: it can set up entry hazards such as Spikes and Stealth Rock, cripple the opponent with Thunder Wave and Toxic, mitigate its lack of a reliable recovery move with Leech Seed, Substitute, and Protect, and even set up with Curse. Ferrothorn is not invincible, though: a neutrality to Ground and a weakness to Fighting greatly hamper its physical walling capabilities. Powerful Fire-types such as Heatran and Infernape can easily incinerate Ferrothorn with their STAB attacks. This glaring quadruple weakness is also an invitation for many special sweepers that are otherwise helpless against Ferrothorn, such as Latios and the aforementioned Starmie and Rotom-W, to surprise it with Hidden Power Fire.
Forretress
Type: Bug / Steel
Base Stats: 75 HP / 90 Atk / 140 Def / 60 SpA / 60 SpD / 40 Spe
Abilities: Sturdy / Overcoat (Unreleased)
Forretress, the premier spinner of DPP, may have gained little this generation outside of a buffed Sturdy, but he still retains a very useful niche in the BW OU metagame. Access to all entry hazards and the ability to Rapid Spin go a long way toward making Forretress a virtual necessity for any stall team; an impressive physical Defense and salvageable Special Defense allow him to find a place on many a balanced and even offensive teams as a reliable wall and pivot as well. Indeed, Forretress has far more on his resume than mere hazards work. With his colossal Defense, Forretress can tank most physical sweepers, and retaliate with his surprisingly usable base 90 Attack stat. STAB Gyro Ball along with his dismal Speed allows Forretress to counter many speedy sweepers, most frequently Outrage-locked Dragons, and a buffed Sturdy enables Forretress to abuse Custap Berry—once released—if need be to ensure two hits on a dangerous sweeper. Whether one needs an unbreakable staller, a Rapid Spinner, a clutch counter, or a catch-all defensive giant, look no further than Forretress.
Gastrodon
Typing: Water / Ground
Base Stats: 111 HP / 83 Atk / 68 Def / 92 SpA / 82 SpD / 39 Spe
Abilities: Sticky Hold / Storm Drain / Sand Force
In the massive pool of bulky Water-type Pokemon, Gastrodon has finally received a niche above the others with Storm Drain, which now gives an immunity to Water-type attacks and a +1 boost to Special attack when hit by one. All of the previous benefits of its Water / Ground typing remain, like an immunity to sandstorm damage, and the added bonus of Storm Drain makes it an excellent special wall. Powerful attackers like Rotom-W and Starmie will need to run Hidden Power Grass to leave any lasting damage on this slug. The combination of the new move Scald and Toxic makes bulky Gastrodon fairly hard to switch into. Gastrodon is not only a strong check to rain-abusing sweepers; (replace with semi-colon) with Choice Specs it can be a sturdy cannon itself. If your opponent makes the mistake of hitting that type of Gastrodon with a Water-type attack, even Blissey is looking at a potential 2HKO.
Gliscor
Type: Ground / Flying
Base Stats: 75 HP / 95 Atk / 125 Def / 45 SpA / 75 SpD / 95 Spe
Abilities: Hyper Cutter / Sand Veil / Poison Heal
Gliscor needs no introduction: it is one of the most common sights in the OU metagame simply because it is able to counter and check prominent threats. Terrakion, which general consensus holds as one of the greatest threats in OU, is conditionally countered by it, and Landorus is also beaten unless it has Hidden Power Ice, making it a top-tier counter to offensive sandstorm-based teams. Indeed, perhaps the greatest testament to defensive Gliscor's effectiveness is the sheer number of physical Pokemon that run an Ice move solely for Gliscor: Tyranitar, Mienshao, and Virizion are just a few examples. While Gliscor's Dream World ability is incompatible with Roost, the combination of Toxic Orb + Poison Heal, and possibly even Substitute and Protect, is more than enough for it to last through the game.
Gyarados
Type: Water / Flying
Base Stats: 95 HP / 125 Atk / 79 Def / 60 SpA / 100 SpD / 81 Spe
Abilities: Intimidate / Moxie
Since the release of RSE, when Gyarados recieved Intimidate, Gyarados has been a particularly tough Pokemon to take down. With 95 / 79 / 100 defenses, 5 resistances, (comma) and only 2 weaknesses, (comma) Gyarados can tank a vast amount of Pokemon. Throughout the DPP era, Gyarados was one of the best Fighting-resists in the game, lowering the opponent's Attack just by coming in, (comma) and then either setting up with Dragon Dance or simply tanking them with the combination of Rest and Sleep Talk. However, with Terrakion and Virizion becoming the more popular Fighting-types in BW OU, the RestTalk set has lost a bit of its luster. It is still a threat through its raw defenses and the new move Dragon Tail, which gives it approximately a 2/3 chance to phaze in it's sleep; Gyarados is one the very few Pokemon that can afford to run a RestTalk set with the new sleep mechanics, resetting the sleep timer every time a Pokemon switches out. Substitute + Dragon Dance sets are also good for tanking hits and turn BW's standard bulky Water-types into set-up bait.
Hippowdon
Type: Ground
Base Stats: 108 HP / 112 Atk / 118 Def / 68 SpA / 72 SpD / 47 Spe
Abilities: Sand Stream / Sand Force (Unreleased)
The generation shift has not been especially generous to Hippowdon; however, its value as a physical wall has only increased with the plethora of new physical attackers introduced to the metagame, such as Terrakion and Landorus. With huge HP and Defense stats, Hippowdon is nigh on impossible to take down with a physical attack, and its respectable Special Defense coupled with its great HP allow it to take several special hits with the right investment. A decent support movepool, with options such as Stealth Rock, Roar, Yawn, and Slack Off, further enables Hippowdon to help out its teammates with ease. Hippowdon's ability, Sand Stream, not only allows it to add more residual damage to the tally, but also makes it the perfect partner to a multitude of sand abusers, letting it find a place on all kinds of teams.
Jellicent
Type: Water / Ghost
Base Stats: 100 HP / 60 Atk / 70 Def / 85 SpA / 105 SpD / 60 Spe
Abilities: Water Absorb / Cursed Body / Damp (Unreleased)
BW introduced a very welcome 2-in-1 Pokemon: Jellicent, simultaneously both a bulky Water and spinblocker. Along with Jellicent's unique Water / Ghost typing comes plenty of key resistances and immunities, two usable abilities in Water Absorb and Cursed Body, solid 100 / 70 / 105 defenses, instant recovery, a surprisingly decent offensive movepool, as well as support moves like Taunt, Will-O-Wisp, and Trick Room; in other words, all you could ask for. Jellicent's primary role on a team is typically to render Rapid Spin useless, which is why it is often found paired with a entry hazard layer, most commonly Ferrothorn. The FerroCent core is BW's answer to SkarmBliss: not only do their typings complement perfectly, Ferrothorn also sets up hazards which Jellicent then prevents the opponent from removing. Thanks to these traits, Jellicent can go toe-to-toe with some of the metagame's biggest threats, such as Heatran, Volcarona, Infernape, Mienshao, Terrakion, Swords Dance Lucario lacking Crunch, and Choice Band Scizor, just to name a few. Access to Toxic and Taunt also allow it to fare well against opposing bulky Water-types and walls. Jellicent does suffer from being setup bait for Pokemon such as ChestoRest variants of Volcarona, Nasty Plot Celebi, is largely shut down by faster Taunters like Whimsicott, and cannot stand up to the sheer power of the likes of Choice Specs Latios and Choice Band Haxorus. Nonetheless, if you need a solid defensive spinblocker and utility counter, this is the jellyfish for you.
Jirachi
Type: Steel / Psychic
Base Stats: 100 HP / 100 Atk / 100 Def / 100 SpA / 100 SpD / 100 Spe
Ability: Serene Grace
Thanks to its large HP and balanced defensive stats, which are some of the most impressive in standard play, as well as its excellent defensive typing, Jirachi easily presents an insurmountable roadblock to thwart many an impending sweep. Jirachi is far from a passive sponge, however: its wide movepool allows it to be an extremely dynamic Pokemon. Jirachi is often seen spreading paralysis using either Thunder Wave or Body Slam, the latter of which has a 60% chance of paralysis thanks to Serene Grace. As a Normal-type attack, this gives Jirachi a niche ability to paralyze Ground-types. Jirachi is also an excellent team supporter with dual screens, Trick Room, or even Gravity, as it has U-turn to conserve momentum after setting up. Its Steel typing and immense special bulk further lets it check Dragon types, particularly Latios, sponging even Choice Specs Draco Meteors with ease. However, the main draw of defensive Jirachi is Wish. A multitude of resistances, great bulk, and the ability to outspeed a variety of threats even without investment lets Jirachi replenish its own health or that of a teammate reliably throughout the match. This variant of Jirachi often maximizes investment on its already large base HP stat to further enhance its capabilities, as with the new Wish mechanics, Jirachi's 202 HP Wishes can often revitalize a teammate worn down by hazards, Life Orb recoil, or an untimely misprediction. Jirachi's ability to render damage to the rest of its team null and void is what makes it such a defensive threat: be sure to pack powerful Fire- or Ground-type attacks to deal with the star, as it is notoriously difficult to 2HKO otherwise.
Latias
Type: Dragon / Psychic
Base Stats: 80 HP / 80 Atk / 90 Def / 110 SpA / 130 SpD / 110 Spe
Ability: Levitate
Despite losing Soul Dew in the generation shift, Latias still functions excellently as a special wall in standard play with her massive base 130 Special Defense, as well as neat resistances to Water-, Fire-, Electric-, Psychic-, and Fighting-type attacks. Wish Latias in particular partners very well with Ferrothorn: each covers the other's resistances almost flawlessly. Besides being able to pass Wish, Latias has access to Recover and Roost as well, allowing it to regain health in a single turn rather than two. This makes a bulky Calm Mind set an excellent choice for Latias, letting her boost her impressive Special Defense to outstanding levels and enabling her to hit very hard with STAB Dragon Pulse; Substitute, Wish, Roar, and Refresh all have good utility on this set for a variety of reasons. Finally, Latias can also be more of a team player by running an effective dual screens support set, making use of her great bulk and multitude of resistances to come in repeatedly during the match to perform her job.