Blaziken
Blaziken was gifted with the amazing ability Speed Boost from Gamefreak's Dream World and was quickly banned due to its influence. By increasing its speed every turn it could potentially snowball to the point where it would be impossible to revenge kill. Combine that with Swords Dance and you have one of the mightiest sweepers of the Dream World tier on your hands. Blaziken especially excels on Sun Teams, who's Drought boost turns his Flare Blitz into an impossibly hard hitting move, which crushes even bulky resists like Jellicent and Gyarados. In the Dream World Blaziken also has access to the move Baton Pass; this lets it pass all of those accumulated boosts and pass them to another pokemon who could then easily sweep. Blaziken does however need to be careful of certain threats; Adamant +2 Blaziken is still outrun by an Adamant Excadrill in the Sand and Choice Scarf Ditto can turn an almost assured sweep into a very dangerous situation.
Raikou
Raikou is given the ability Volt Absorb in the Dream World and with that it is given a new lease on life. Volt Absorb is incredibly useful as it helps Raikou stop two huge influences of the Dream World meta; Thundurus and Volt Switch. Raikou has the satisfaction of being one of the few true counters to Thundurus. It can survive any hit from the Nasty Plot boosted Genie and quickly revenge kill with its powerful STAB Electric-type attacks, it doesn't even need to worry about any crippling Thunderwaves. Raikou can even be a solid answer to Volt-turn teams, it can come in on Rotom's Volt Switchs and proceed to severely dent any pokemon coming in. It can even use Hidden Power Fire to stop the Steel/Bug-type pokemon who tend to accompany Rotom-W.
Scrafty
Scrafty is a pokemon known for its top-notch abilities and thanks to Dream World it can add another one onto its resume, Intimidate. Intimidate is widely regarded as one of the most powerful and influential abilities a pokemon can have, lowering the Attack Stat of the opponent's pokemon when switching in. This grants Scrafty numerous new opportunities to begin setting up with moves such as Bulk Up or Dragon Dance. A Scrafty with two Dragon Dances under its belt is not hard to imagine thanks to Intimidate and its awesome natural bulk; Scrafty is definitely not a threat to be forgotten in the Dream World tier.
(Lemme know if I should add anything, especially for Scrafty. Didn't have a whole lot to say for him :)