Well, Nintendo has been pushing this style of deck on us for a while but only now can it even be considered viable, thanks mostly to Exploud doing tons of damage with it. The focus of this deck is the Round attack, which is more powerful the more Pokemon who have it.
x3 Whismur: http://serebii.net/card/plasmastorm/105.shtml
-Needed for evolution. At least it can discard I guess.
x3 Loudred: http://serebii.net/card/plasmastorm/106.shtml
-Needed for evolution.
x3 Exploud: http://serebii.net/card/plasmastorm/107.shtml
-A very powerful Pokemon. With just three other Pokemon in play with the Round attack, Exploud can take down any foe, even Wailord. It also will be staying in for quite some time thanks to 140 HP, which is good since that four retreat cost means it won't be leaving any time soon.
x3 Jigglypuff: http://serebii.net/card/nextdestinies/078.shtml
-Needed for evolution.
x2 Wigglytuff: http://serebii.net/card/nextdestinies/079.shtml
-Honestly it's really only there for Round. Its Round can only do up to 120 damage (which is okay I guess, especially for one DCE) but really this guy is only there to power up Exploud or even Meloetta.
x4 Meloetta EX: http://serebii.net/card/shinycollection/011.shtml
-The only basic with access to Round. While it might be weak for an EX, this alone makes it have an important place in the deck. I can just slap it down to power up Exploud.
x3 Kangaskhan: http://serebii.net/card/battlestrengthdeckblastoisekyuremex/007.shtml
-A great basic to hold the line while I build up my Pokemon with Round. Kangaskhan even helps with the build up through its Call for Family attack, which gets me basics. This includes Meloetta EX. Comet Punch is also solid, doing up to 80 damage for one DCE.
x4 N: http://serebii.net/card/noblevictories/092.shtml
x4 Cheren: http://serebii.net/card/emergingpowers/091.shtml
x4 Pokemon Catcher: http://serebii.net/card/emergingpowers/095.shtml
-Gets out the Pokemon I want.
x4 Skyla: http://serebii.net/card/boundariescrossed/134.shtml
-Gets me the trainers I want.
x4 Silver Mirror: http://serebii.net/card/megalocannon/069.shtml
-Exploud does the damage of an EX card. Now it doesn't take any damage from EX cards.
x3 Pokemon Communication: http://serebii.net/card/blackwhite/099.shtml
-Gets me the Pokemon I want.
x2 Switch: http://serebii.net/card/blackwhite/104.shtml
-As I said, Exploud has a ghastly retreat cost.
x1 Computer Search: http://serebii.net/card/boundariescrossed/137.shtml
-Gets me the card I need.
x9 Psychic Energy
x4 Double Colorless Energy: http://serebii.net/card/nextdestinies/092.shtml