There are lots of helpful Pokemon TCG cards.
Kyurem (Noble Victories 34)
Kyurem can help damage Pokemon. With its Glaciate attack, Kyurem does 30 damage to each of your opponents Pokemon, including the active. that can knock out Pokemon such as Magikarp and Solosis
Landorus (Noble Victories 74)
If you need energy, and you have a lot of them in your Discard Pile, Landorus is helpful. When Landorus uses its Abundant Harvest attack, you can attach an energy from your discard pile to your Basic Pokemon. Also, you can still attach the energy from the, "1 Energy For Each Turn" rule.
Reshiram (Black and White 26,113, BW Promo 004)
Reshiram is helpful, for its Blue Flare attack. Though you have to discard 2 {R}, you can still use Landorus's Abundant Harvest attack to get energy back on to Reshiram to attack again. Blue Flare does 120 damage, knocking out most Basic Pokemon, some Stage 1, and some Stage 2 Pokemon.
Tornadus (Emerging Powers 89, 98)
Tornadus can help you move energy around and do damage at the same time. Energy Wheel lets you move 1 energy from 1 of your benched Pokemon to your active Pokemon. Hurricane does the opposite and also does 80 damage.
Virizion (Emerging Powers 17), Terrakion (Emerging Powers 63), and Cobalion (Emerging Powers 77)
Virizion, Terrakion, and Cobalion are useful for their Sacred Sword attack. it does 100 damage. but, you can't use Sacred Sword the next turn. This knocks out most Basic Pokemon, and a few stage1 Pokemon.
Victini (Noble Victories 15)
Victini can do really quick damage. In 2 turns, Victini can do 100 damage with V-Create, but you need to have at least 5 benched Pokemon. that means in 3 turns, Victini can do 200 damage!
Mewtwo EX (Next Destinies 54)
Mewtwo EX has a very powerful Psydrive attack. It does 120 damage, but you have to discard 1 energy from Mewtwo EX. Since you can attach 1 energy per turn, you can do 120 damage each turn! That means in 2 turns, you can knock out any Pokemon!
Blaziken (Dark Rush 12)
Blaziken has an extremely powerful attack. It's Flamethrower. you can do 130 damage for 3 energies, but you have to discard 1 energy attached to Blaziken. Since you can attach 1 energy per turn, you can knock out any Pokemon in 2 turns!
Pokemon Catcher (Emerging Powers 95, Dark Rush 76)
Pokemon Catcher is really a great card and expensive. It lets you switch your opponent's defending Pokemon with 1 of their benched Pokemon.
Emboar (Black and White 19)
Emboar is a great card because you can do 150 damage with its Flare Blitz attack. After you attack, you also have to discard all {R} from Emboar. Also, it's HP is high with 150 HP. Its high HP lets this card stay out for a lot of turns.
I hope this guide really helps you on helpful and useful cards in the Pokemon TCG.
Kyurem (Noble Victories 34)
Kyurem can help damage Pokemon. With its Glaciate attack, Kyurem does 30 damage to each of your opponents Pokemon, including the active. that can knock out Pokemon such as Magikarp and Solosis
Landorus (Noble Victories 74)
If you need energy, and you have a lot of them in your Discard Pile, Landorus is helpful. When Landorus uses its Abundant Harvest attack, you can attach an energy from your discard pile to your Basic Pokemon. Also, you can still attach the energy from the, "1 Energy For Each Turn" rule.
Reshiram (Black and White 26,113, BW Promo 004)
Reshiram is helpful, for its Blue Flare attack. Though you have to discard 2 {R}, you can still use Landorus's Abundant Harvest attack to get energy back on to Reshiram to attack again. Blue Flare does 120 damage, knocking out most Basic Pokemon, some Stage 1, and some Stage 2 Pokemon.
Tornadus (Emerging Powers 89, 98)
Tornadus can help you move energy around and do damage at the same time. Energy Wheel lets you move 1 energy from 1 of your benched Pokemon to your active Pokemon. Hurricane does the opposite and also does 80 damage.
Virizion (Emerging Powers 17), Terrakion (Emerging Powers 63), and Cobalion (Emerging Powers 77)
Virizion, Terrakion, and Cobalion are useful for their Sacred Sword attack. it does 100 damage. but, you can't use Sacred Sword the next turn. This knocks out most Basic Pokemon, and a few stage1 Pokemon.
Victini (Noble Victories 15)
Victini can do really quick damage. In 2 turns, Victini can do 100 damage with V-Create, but you need to have at least 5 benched Pokemon. that means in 3 turns, Victini can do 200 damage!
Mewtwo EX (Next Destinies 54)
Mewtwo EX has a very powerful Psydrive attack. It does 120 damage, but you have to discard 1 energy from Mewtwo EX. Since you can attach 1 energy per turn, you can do 120 damage each turn! That means in 2 turns, you can knock out any Pokemon!
Blaziken (Dark Rush 12)
Blaziken has an extremely powerful attack. It's Flamethrower. you can do 130 damage for 3 energies, but you have to discard 1 energy attached to Blaziken. Since you can attach 1 energy per turn, you can knock out any Pokemon in 2 turns!
Pokemon Catcher (Emerging Powers 95, Dark Rush 76)
Pokemon Catcher is really a great card and expensive. It lets you switch your opponent's defending Pokemon with 1 of their benched Pokemon.
Emboar (Black and White 19)
Emboar is a great card because you can do 150 damage with its Flare Blitz attack. After you attack, you also have to discard all {R} from Emboar. Also, it's HP is high with 150 HP. Its high HP lets this card stay out for a lot of turns.
I hope this guide really helps you on helpful and useful cards in the Pokemon TCG.