HP:100 Attack:60 Defence:70 Special Attack:85 Special Defence:105 Speed:60
A very nice Bulky Water and arguably the best spin blocker in OU now that the Rotom Formes have been liberated of their Ghost typing, Jellicent is a solid choice of tank on most teams. Excellent typing and a great support movepool all contribute to its success, but it's the synergy it has with Ferrothorn that really brings out the best in it.
Playing with Jellicent:
Jellicent is primarily played as a typical Bulky Water, with defensive EVs, instant recovery, and other support moves. One major perk that Jellicent gets is STAB Scald, which roles its offensive option and status move into one thanks to it's high burn rate. This either leaves more room on the moveset for additional support options, or allows you to carry multiple status attacks. Jellicent can make excellent use of either ability, with Water Absorb healing you on occasion and Cursed Body potentially saving you from being 2HKO'd through lucky disables.
Playing against Jellicent:
While a perfectly decent tank, it's defences aren't the highest in the game and can typically be overwhelmed by super effective moves with ease. Thundurus, for example, can shut it down with Taunt or just destroy it with STAB Thunderbolt. Grass types fare even better with their Water resistance. It also falls to Toxic without external support, allowing stall teams to best it with Toxic Spikes.
HP:74 Attack:94 Defence:131 Special Attack:54 Special Defence:116 Speed:20
Here we have it, the new king of OU. Ferrothorn has reigned at the top of OU usage statistics since the introduction of competitive 5th gen play, and with good reason. Absolutely stellar stats in all the right, excellent typing, anda movepool with everything you could need bar instant recovery. Ferrothorn is quite literally the thorn in most players' sides.
Playing with Ferrothorn:
Ferrothorn is first and foremost a wall, as evidenced by its sky high defences. Capable of taking hits on both sides of the spectrum, it makes an effective check to many threats. While it certainly isn't without counters, it does force plenty of switches, giving it time to set up different types of entry hazards or throw out status moves or Leech Seed. It's certainly no offensive slouch either, capable of throwing out strong STAB Power Whips and Gyro Balls. Latent damage from Iron Barbs certainly doesn't hurt either. One key way to make the most out of Ferrothorn is to use it in the rain, neutering the quad weakness which is one of the few things holding it back from true godliness.
Playing against Ferrothorn:
It's quite obvious, but outside of rain Ferrothorn is destroyed by Fire attacks. Not even defensive stats like these counteract a quadruple strength fire move from even a moderately powerful foe. Conkeldurr can potentially use Ferrothorn as setup bait, it doesn't fear it's attacking options after a couple of Bulk Ups, welcomes Thunder Wave and counteracts Leech Seed with boosted Drain Punches. Tricking a choice item over to Ferrothorn will also completely cripple it.
HP:60 Attack:55 Defence:90 Special Attack:145 Special Defence:90 Speed:80
Chandelure is the single most powerful special attacker outside of Ubers, nothing else generates as much raw power at this monster. Worse still, it can generate even more power through the use of Calm Mind or Flash Fire, and it's decent base 90 defences offer ample opportunity to switch in. A decent base 80 speed and a great movepool round out this excellent sweeper. Now all we need is it's Dream World ability and we can ship it off to Ubers.
Playing with Chandelure:
While capable of running many sets, they all have the same end goal- hit things, and hit them bloody hard. Most Chandelure sets revolve around maximised special attack and speed, and the moves Fire Blast and Shadow Ball. From here they diverge into sets running Calm Mind, SUbstitute, or Choice attacks, with sub and choice sets being the most successful. However if you have the Sun on your side as well, get ready to watch this thing tear virtually anything apart, even 2HKOing Blissey without any other kind of boost.
Playing against Chandelure:
Heatran is an all star counter, resisting it's STAB moves and outspeeding, with Earth Power to KO with. Porygon2 with Trace boasts the same advantages switchin in, albeit without a way of retaliating, which is enough to force a switch in most sets for fear of status. Politoed and Tyarnitar can both abuse their weather to neuter STAB Fire Blasts, with TTar having the same qualities in it's typing as Heatran and Porygon2. Finally it is, once again, easy to revenge kill with it's middling speed.
HP:76 Attack:147 Defence:90 Special Attack:60 Special Defence:70 Speed:97
The antithesis of Reuniclus, Haxorus was a Pokemon everybody expected to immediately begin dominating everything, but surprisingly didn't. While it's attack stat is truly monstrous, with access to STAB outrage, a limited movepool and suckish speed tier (If you hadn't noticed by now, speed is exceedingly important in 5th gen OU) held it back from being the driving force everybody was anticipating. That said it's still a great sweeper with access to both Dragon Dance and Swords Dance, and should be rightfully considered when building a team.
Playing with Haxorus:
Sweeping is the only way to go with Haxorus, with either a boosting move for full sweeps or a choice items for more focused damage. As powerful as it is, Haxorus is stopped cold by steel types like Skarmory, but unlike Excadrill it is actively at risk of being beat one-on-one by Brave Bird. Fielding a trapper like Dugtrio, Magnezone or Wobuffet is therefore essential for making the most out of Haxorus. Entry hazards are also highly recommended, because while it has no trouble OHKOing large quantities of things, it is quite frail itself and cannot risk being caught off guard by stray focus sashes.
Playing against Haxorus:
Bulky, floating Steel types are the bane of Haxorus, because unlike other dragons it lacks Flamethrower or Fire Blast for assaulting their weaker stat. Not that it matters too much, given it's pathetic Special Attack stat. Ferrothorn copes similarly welll with it's Eathquake neutrality and all manner of moves to screw Haxorus over. And, once again, Haxorus is easily revenge killed.
If there's one thing 5th gen has been good for, it's introducing new fighting types. Mienshao is one of the few to be a traditional sweeper, rather than a tank like Conkeldurr and Scrafty. With a decent speed, wide movepool and great stats for either a physical or mixed attacker, Mienshao isn't short of options, and can catch a lot of people off guard.
Playing with Mienshao:
The most popular way of using Mienshao has proven to be a set which can abuse the synergy between Life Orb and it's ability Regenerator. A set which seeks to immediately cause damage with a powerful STAB high jump kick is most common, often coupled with U Turn for causing damage as well as activating the health boost. However a more aggressive Swords Dance and Choice sets have also proven popular, with Hidden Power to deal with Gliscor in a similar manner to how MixApe functioned last generation. Lead sets are also successful, with a powerful Fake Out and well as a quick Taunt.
Playing against Mienshao:
Mienshao likes to move around a lot, making status the best way to deal with him. Entry hazards, particularly spikes, also help counteract the healing it gets upon switching out, reducing its longevity. If you can hit it with paralysis or a burn, it becomes a hell of a lot more manageable, or at very least reduces the sting in his tail. Another excellent way would be force it to crash when using it's STAB of choice, High Jump Kick. While it is more accurate than last gen and the punishment arguably less severe, it is still easy to abuse with decent prediction and the use of Protect and Ghost types.
HP:92 Attack:105 Defence:90 Special Attack:125 Special Defence:90 Speed:98
This generations pseudo legendary, and the first to have a special bias, Hydreigon is quite a force in the metagame. With an excellent suite of resistances and immunities, Hydreigon has ample opportunities to switch in and raise hell. With an excellent all around stat line and varied movepool, Hydreigon can pull of multiple different sets to good effect.
Playing with Hydreigon:
Offence is the way to go with Hydreigon, with STAB Draco Meteor being something to abuse on pretty much every set. Given the synergy between Fire and Dragon moves, Hydreigon can often cover the entire metagame in just half of its moveset. This leaves room for Dark Pulse as a secondary STAB, Dragon Pulse for a more consistent STAB, or U Turn for hitting special walls for damage as you escape. Choice items or Life Orb are typically the items of choice to capitalise on the raw power that Hydreigon can generate, however leftovers can be used on rarer, albeit viable, defensive sets.
Playing against Hydreigon:
You may have noticed a trend in my suggestions for Pokemon under base 100 speed, they're all easy to revenge kill. Hydreigon especially so, given it's complete lack of boosting moves. Hydregion may have a lot of opportunities to switch in, but it's dark typng introduces additional weaknesses, most notable to Fighting, also making it susceptible to the ever common Mach Punch. Dedicated special walls, well, wall it, given it's inability to boost to a higher threshold to gain 2HKOs, forcing it resort to U Turn which often sees little EV investment.
HP:85 Attack:60 Defence:65 Special Attack:135 Special Defence:105 Speed:100
Of all the new Pokemon release this generation, Volcarona is one of the most threatening. Excellent typing and stats are a great start, coupled with an impressive movepool. While not particularly varied, it gets all the tools it needs to become a nightmare in multiple roles, most notable Quiver Dance and Fiery Dance. Quiver Dance, a move Volcarona is the exclusive user of in OU, is like a beautiful love child of Dragon Dance and Calm Mind, raising SpAtt, SpDef and Speed by one stage. A quick glance at Volcarona's stat line reveals it gains boosts in it's three best stats, and after a couple of boosts very little can dent Volcarona's special defence, if it is even allowed to live long enough to attack. Fiery Dance is Volcarona's signature move, and is essentially a weaker version of Flamethrower with a 50% chance of getting a Special Attack boost. Between these two moves Volcarona can become a viciously powerful sweeper, one that gets to boost every time it uses its STAB.
Playing with Volcarona:
As mentioned above, a Quiver Dance set is truly impressive when used correctly, and typically the way to go with Volcarona. Bug Buzz and Hidden power typically round out the set for maximum coverage. However bulky Quiver Dance sets can also be highly effective, with HP and Defence maximised making it surprisingly bulky, and after a QD it's very difficult to OHKO on either side of the spectrum without a super effective STAB attack. This set can also make use of Will O Wisp or Morning Sun to make killing it even more problematic. Alternatively choice sets are effective, and can still get boosts from the ever useful Fiery Dance.
Playing against Volcarona:
As powerful as Volcarona is, it is not without it's flaws. The glaring one is Rock types, in particular Stealth Rock, which sheds 50% of it's HP upon switching in. Weather can also severely limit it's effectiveness, with Rain neutering it's Fire STAB and sand providing 50% SpDef boosts to the Rock types best equipped to kill it. Alternatively most special walls can overcome Volcarona before it can boost high enough to 2HKO them.
HP:91 Attack:129 Defence:90 Special Attack:72 Special Defence:90 Speed:108
We now arrive at the first new legendary to make it into OU, and it's a hell of a good one. Terrakion has proven itself as one of the best physical attackers of the new generation, and even in the entire game. A huge attack stat, high speed, great STABs, and excellent movepool all make for an extremely threatening sweeper.
Playing with Terrakion:
Making the most out of Terakion is quite simple- increase your Attack or Speed, start killing things. The most popular set is the doubler dancer, which uses both Rock Polish and Swords Dance in conjunction with dual STAB moves. Rather than attempting to get one boost of each (Although if this does happen, the better), it simply revolves around getting one of which ever boost is preferable; after a Rock Polish almost nothing can catch it, allowing it to work its way through offensive teams, while a Swords Dance allows it to crush all but the most defensive walls. Choice items achieve a similar effect while allowing for more move variety at the expense of not being able to tear through entire teams in one fell swoop.
Playing against Terrakion:
Priority is the best way to go, given that it will spend a lot of time outspeeding your entire team. Whether it's priority attacks like Mach Punch or Aqua jet, or priority status from Thundurus or Whimsicott. The latter two may die as a result, but they allow you to at least revenge kill it. Gliscor is one of the few Pokemon who can survive a +2 Stone Edge and Close Combat, and can retaliate with Earthquake. A Quagsire running unaware can also tank most hits at least once, once again having a STAB Earthquake that can potentially KO after Close Combat's defence drops. But the fact that I can name such a specific set of Pokemon should indicate how substantial a threat this thing can be if it gets to set up.
HP:91 Attack:90 Defence:72 Special Attack:90 Special Defence:129 Speed:108
Virizion has found it's niche as an all encompassing check to weather in OU. With resistances to Rock, Ground, Water and Electric, it can happily switch into the most common moves of Sand and Rain teams, taking little damage and retaliate well with its impressive combination of bulk and speed. With a varied movepool on both sides of the spectrum, Virizion is capable of be tailored to your specific needs.
Playing with Virizion:
Virizion is typically employed to abuse the easy switches weather teams provide and set up either Calm Mind or Swords Dance. Calm Mind aids its ability to take on rain teams even further, with STAB Giga Drain to replenish health from the multiple water types available, while Swords Dance is better against sand given that it does not have to content with SpDef boosts of rock types. Support sets are viable, with plenty of status options and even dual screens, but these roles are often performed better by other Pokemon.
Playing against Virizion:
While Virizion is typically an excellent stop to rain teams, Hurricane is rising in popularity now, and without a couple of CMs Virizion is not going to be taking a base 120 quadruple strength attack. Other flying moves are equally effective, with an unencumbered Acrobatics being more effective as it has no way of bolstering it's physical bulk. Psychic moves have a similar effect, Psycho Shocks from the Lati Twins and Reuniclus in particular.
HP:79 Attack:115 Defence:70 Special Attack:125 Special Defence:80 Speed:111
While often deemed inferior to the other genies, Tornadus is arguably more versatile and quite capable of being deadly. With a great movepool complemented by excellent stats and the ever useful Prankster, Tornadus can perform in all manner of roles.
Playing with Tornadus:
Tornadus is often played to abuse either of it's two excellent STABs, Hurricane and Acrobatics. Both of these moves are obscenely powerful in the right conditions, and complemented by other attacks it has access to such as Hammer Arm and U Turn. Prankster is also capitalised on in most sets, whether it's taunting opposing walls, as well as setting up fast Rain Dances or Tailwinds.
Playing against Tornadus:
Tornadus is quite a difficult Pokemon to counter in the strictest sense of the word. It fends off attempts to status it with Taunt and has enough attacking power and speed to maim most things that attack it. The best way would be to outspeed and hit it for super effective damage, which isn't a massive issue given the rarity of Choice Scarf sets. Priority Ice Shard also typically kills it, given that Ice Shard is almost always backed up by STAB. Figuring out whether it's physically or specially biased also makes walling it easier, given that it lacks any kind of boosting moves.