These Pokémon make up popular decks in TCG Pocket at the moment.
Pikachu EX: Relies on a bench full of other electric types to use; otherwise, it deals zero damage.
Mewtwo EX: The go-to psychic combo. Mewtwo destroys two turns worth of energy to use it's strongest attack, and gardevoir provides an extra turn's worth of energy for free. So gardevoir lets it spam it infinitely
Moltres EX: uses an ability to generate 0-3 mana based on coin flips to empower other pokemon in the back line. obviously, 3 tails means you get jack shit.
Dragonite: Very powerful and very fun, but the only current deck that requires splitting your energy type, which makes it a real crapshoot. with no reliable way to generate either energy, you're stuck with the luck of the draw.