A personal Top 10 list of mine:
1. Emolga: Call for Family is one of the best (if not the best) set-up moves in the game.
2. Blend Energies: These were clearly designed with Dragons in mind, as most Dragons can take advantage of two of the four types on a Blend Energy rather than using one from each. GRPD is slightly better because it can be moved via Dark Trance.
3. Hydreigon (Dark Trance): This is like Klinklang, but better. Why? Because Darkness types have loads more support than Metal types, such as Darkrai EX's Dark Cloak and Dark Patch. For those that are in the dark on this one, Dark Trance lets you move your Darkness Energy to any Pokemon you want, similarly to Klinklang's Gear Shift.
4. Terrakion EX: Another addition to our many great Energy accelerators, such as Eelektrik, Emboar, and Dark Patch. For those that don't know, for (FFC), Pump-up Smash does 90 damage and attaches 2 Basic Energies from your hand to your Benched Pokemon in any way you like.
5. Mew EX: Versatility is a great thing on any card, and this one is no exception. Its Ability (aptly named Versatile) allows it to use an attack of any Pokemon in play. This allows for some insane combos that would otherwise be impossible. The only real downside is its extremely low HP for an EX combined with the 2 Prize drawback.
6. Rayquaza: Although being printed as a secret rare is unfortunate (and has never been done before), that doesn't make the card any less playable. Shred OHKOes any Dragon type before Giant Cape (Eviolite is still a OHKO). Great as a Sigilyph killer in mono-EX decks as well.
7. Garbodor: This living trash bag is most certainly not trash. Garbotoxin works as long as a Pokemon Tool is attached to Garbodor and nullifies all other Abilities that aren't named Garbotoxin. If a deck that uses it effectively can be found, it would make a great anti-meta; the problem is it needs to be a deck that can operate without Abilities.
8. Registeel EX: Triple Laser is a great spread attack and is splashable thanks to only needing Colorless energy.
9. Sigilyph: The only true EX wall in the entire format.
10. Rayquaza EX: Dragon Burst is very powerful and combos with both Emboar and Eelektrik.
Runner Up: Giratina EX: The only EX in the game that can kill Sigilyph via Shred. Possibly splashable into Darkrai/Hydreigon due to Blend GRPD support.