Deoxys-S
The premiere hazard setter from Standard OU is still around here in Dreamworld, and is still as unpredictable as ever with the greatest support movepool in the game. Access to Stealth Rock, Spikes, Taunt, Reflect, Light Screen, Rain Dance and Sunny Day really diversify Deoxys-S and make it a really dangerous opponent to face. Deoxys-S also has a wide attacking movepool to delve into, surprising a ton of switch-ins with attacks like Ice Beam, Focus Blast, Superpower, Psychic and Thunderbolt. Deoxys-S is one of the most threatening Pokemon in the metagame so caution must be taken when it is sent out by your opponent. There are a few things that will stop Deoxys-S short from setting up full Spikes or dual screens like Thundurus and other pranksters, which will always outspeed with Taunt and shut Deoxys-S down. Since Deoxys-S serves a sort of "Suicide Hazard/Screens Setter" role there are a few other ways to clear out the hazards and screens Deoxys-S has set, like Rapid Spinning right after Deoxys-S is dead and Brick Breaking while Deoxys-S is setting up screens.
Thundurus
The thunder genie makes a spash in Dreamworld, boasting very good 115 / 125 offenses, Thundurus hits very hard right off the bat. With a great ability in Prankster and access to key moves in Thunder Wave, Taunt, Substitute, Toxic and the great Sp. Atk boosting move Nasty Plot, Thundurus gets the jump on faster opponents, especially ones that are scarved. Thundurus also has a very good Speed Stat at Base 111, outspeeding Gengar, Keldeo, Terrakion, Garchomp, Latios and Latias and smacking them with powerful attacks in the name of Thunder and HP Ice. Thundurus also can use Volt Switch in order to scout the opponent, but needs to be careful of Ground-types like Quagsire, Gastrodon and Excadrill switching in for free and completely walling Thundurus. Thundurus can, however, carry Hammer Arm and be able to dispatch Excadrill switch-ins expecting Volt Switch. Either way, Thundurus is a prominent threat in Dreamworld OU and should be played against with extreme caution.
Manaphy
The most dangerous Pokemon under rain must always be treated as a kill as soon as possible threat. With the ability Hydration and access to Rest, Manaphy gets free instant recovery under rain, allowing it to stay in battles much longer than other sweepers. Manaphy also has access to two great boosting moves in Calm Mind and Tail Glow, both making Manaphy a dangerous threat once it gets a boost. Access to Surf and Ice Beam give Manaphy great coverage but not perfect coverage, leaving her completely walled by Jellicent, even with plenty of boosts under its belt. Other ways Manaphy can be dispatched are fast Thunders from Thundurus before it gets too many Calm Minds or simply changing the weather on it, disallowing instant recovery. Even outside of weather Manaphy must still be treated with extreme caution as once Manaphy acquires enough boosts your game is pretty much over.
Excadrill
Excadrill is a sand team's crux, becoming the fastest Pokemon in the game thanks to the ability Sand Rush and bolstering a very threatening Attack Stat on top of it. Excadrill has a limited movepool but pseudo-Edgequake coverage and access to Rapid Spin and Swords Dance more than make up for it. Excadrill can easily perform a Rapid Spin as any Ghost-types that attempt to spin block will be easily KO'd by Rock Slide, especially after a Swords Dance boost. This makes Excadrill a very good team supporter along with a potent sweeper and revenge killer when the situations arise. Breloom easily checks Excadrill with Technician boosted Mach Punch and Gliscor and Skarmory can wall Excadrill and kill or shuffle it out. Another way to stop Excadrill is to simply change the weather on it, bringing its speed back to the abismol Base 88 and opening up many more checks to dispatch this monster. Even though there are a variety of ways to try and stop Excadrill, one must be extremely careful when seeing it on your opponent's team, as it is one of the top threats in the meta for a reason.
Venusaur
Venusaur is blessed with quite a few perks that make it a very useful Pokemon for Sun teams. The ability Chlorophyll doubles Venusaur's Speed stat making him a threatening attacker to face. Growth boosts both of Venusaur's Attacking stats making it a potent sweeper of sorts, and with access to Giga Drain Venusaur is going to stay around for a while. Venusaur has a very diverse movepool to tap into, with access to Substitute, Leech Seed, Sleep Powder, Sludge Bomb, and Hidden Power Fire, it covers its bases well. Venusaur can be much more manageable after Sleep Clause has been enabled and Pokemon like Heatran and Blissey can easily wall Venusaur, although Blissey must be careful of a mixed set. Changing weather and using Prankster Thunder Wave are also ways to make Venusaur more manageable, but one must still be careful switching Politoed and Tyranitar in fearing Venusaur's strong Grass attacks.
Pinch Berries
The integral stat boosting berries are an underrated threat in the Dreamworld tier, allowing every pokemon to receive a free stat boost when below 25% health. There are nine total but only three will see use, being Petaya, Liechi and Salac, raising Special Attack, Attack and Speed respectively. What makes these berries so underrated is that all you have to do is sub up for three turns in order to activate them. Some prime examples of Pinch Berry users from DPP include SubPetaya Empoleon and Drifblim. Although the Pinch Berries are not widely used in the metagame they should still be treated with caution, due to the surprise of turning one of your checks into death fodder.
Shadow Tag and Shed Shell
Upon receiving Shadow Tag as its Dream World ability, Chandelure has made a huge impact on the metagame by being able to trap any Pokemon it switches in on. With an ability like this, the item Shed Shell becomes a very enticing option for quite a few pokemon like Blissey, Skarmory, Breloom and others, just for fear of being a free kill or complete set-up bait. Sacrificing key recovery from leftovers or power boosts from Life Orb is a wise decision when your pokemon really can't do anything to Chandelure, and will easily die in Skarmory's and Breloom's cases or be total set up bait in Blissey's case. Shed Shell allows these key pieces of your team to switch out scot free and allow you to switch in something that will threaten Chandelure. Two common Pokemon that can completely stop Chandelure are Tyranitar and Heatran. Tyranitar cannot easily be KO'd by Chandelure's Fire Blast even with boosts and it can trap Chandelure with Pursuit, while Heatran can snag a flash fire boost and force Chandelure out. When battling, taking away Chandelure's top roles will definitely give you the upper hand in the match. One additional thing to keep in mind with Shadow Tag is when the rare event of Shadow Tag versus Shadow Tag happens, you can freely switch out to a safe Chandelure check without the need for a Shed Shell.