It depends on your deck. Some techs include:
Glalie (SV) (Already mentioned) - It's attack only costs 2 colorless energies, so it's an easy fit in many decks. Just make sure you play enough stadiums. Since it's Water type, be careful about activating Vapor Kick.
Empoleon FB (Already mentioned) - If you're running an SP deck, this is probably a good fit, especially if you're running SP Energy. Again, watch Vapor Kick.
Dewgong SV - It's first attack costs a water and colorless energy, so you may need to dedicate some energy in the deck towards it. It's also a great Donphan counter and decent Machamp counter if you ever run into them. Vapor Kick, while a threat to other Pokemon, only does 30 to Dewgong due to its Thick Fat PokeBody. Dewgong can 2-hit KO Blaziken. And if they Jet Shoot, all you need is some way to do 10 extra damage (PlusPower/Expert Belt/Flash Bite) and you can OHKO Blaziken
Exploud SV - I'm assuming you're having trouble with weakness. This gets rid of it.
Metapod HS - Weakness again, if you're Grass type.
Machamp SF - A classic SP counter. Not an easy fit in many decks, but a beast for SP to deal with nonetheless.