This is draft version.

This is a hybrid between UW Flash and UW aggro. Reason for this is that I want to have as much instant/flash cards as I can get, but also I didn't want to miss Brutal Cathars and Siege Veterans.

Previous iterations of this deck had Secluded Courtyard - but with noncreature instants, those lands are negligible to say the least.

Mainboard contains of 16 flash/instant cards, that interrupt combat and counter opponent's moves. 

We can play it two ways. I know it is very similar, but there are two different mindsets which should be active when playing against given deck.

1. Plain simple aggro - just put as many creatures as we can get, with every window open, pump them, keep counters only to protect board from sweepers.

2. Snowball aggro - play only 'sorcery speed' creatures and attack opponent, keeping instants for control mechanisms (It sounds like strategy #1, but it just is a bit slower - you want to ALLWAYS keep flash/instant ready).

I find it hard to decide If I want to go all-in, or to keep counter/flash ready. This is an issue especially when you have only 1 creature on board and Protect the Negotiators - which may not be enough with its Pay (1) requirement.

Never keep 1-lander. On draw - 2-lander is the best, on play 2-lander is ok, with 3-lander as best option. We can win with 3 lands on board, as 80% of our mainboard is 1-2 mana spells.

How I plan to play against meta:

RB Aggro = your board presence is way better, go-wide and be stable until you put out Skystrike Officer or Harbin, Vanguard Aviator which can end game in few rounds. Counter spells are mostly targeted for bigger threats - Sheoldred, the Apocalypse,Bonecrusher Giant, Graveyard Trespasser // Graveyard Glutton or removal that target your high value creatures.

Mono Green ramp = big Meaty creatures needs to be countered or eaten by Brutal Cathar // Moonrage Brute with other counters waiting for karn, the great reator or Kiora, Behemoth Beckoner as those are main threaths in this deck besides Cavalier of Thorns. I didn't play against it yet, but I think that we need to push as much damage early as possible and interrupt their 'big payoffs' on turns 4+. Hopefully you can push out that damage.

Spirits (all of them) = Spirits have many annoying tools to interrupt our plays. Tap on instant, hexproofing on flash, sacrificing to counter instants, they have their own counters, etc. The thing is that we are wider, and with ANY lord on the board, we can almost always push some dmg in and keep counter for collective company in Bant decks, or for Spell Queller in Azorius spirits.  It's a race, and it is hard to say who is in favor.

Izzet Phoenix = most terryfing is flipping Thing the Ice // Awoken Horror and pushing back our board. It's possible to win this game 1 and WAY easier to win with Rest in Peace after sideboard. Same goes for:

Abzan Greasefang.

Mono White Humans = we play basically mirror, but they have Brave the Elements which can push lethal damage, so be aware that Skystrike Officer generates colorless artifact soldiers! They also play Thalia, Guardian of Thraben which Taxes your counterspells, and is a menace with it's first strike.

UW Control = You won't counter Supreme verdict, so you CANNOT put all creatures on board, you always need to keep something as a backup. Counters are for Teferi, Hero of Dominaria, The Wandering Emperor and hardcasting Shark Typhoon - nothing else. Also be aware how many mana is open on opponents side, so your spells won't be countered. Just push dmg early, and wait for his payoffs. Don't counter his removal spells - you have more creatures than control have removal.