I'd kind of like to discuss Pheromosa, because while I'm very happy myself and about 90 other people bopped it with the ban hammer, there while likely be changes in the metagame that have indirectly buffed or nerfed certain Pokemon.
From what I can tell, Mega Metagross and Greninja are going to get even worse, as Pheromosa was almost always a decent offensive check to Greninja and with the rise of the specs set Metagross as well. No longer does Mega Metagross have to run bullet punch on Mosa weak teams to lure the monster. As well as Greninja, who(while it isn't common) will occasionally run water shuriken to beat Pheromosa. Those of you who are running water shuriken or bullet punch on those Pokemon may now have a move slot free, which is very important to the two most famous cases of 4MSS.
And of course since we are on the subject of controversial Pokemon, it is also worth mentioning that Dugtrio doesn't need to run aerial ace on its scarf set to get rid of Pheromosas not running scarf.
Broken Pokemon aside, Ash Greninja(similarly to its protean counterpart) no longer needs to run water shuriken. Basically, a move slot is freed up. While water shuriken is still a viable option(especially against HO), Pheromosa's ban means that ninja Kermit has two move slots where ice beam, shuriken, u-turn, extrasensory, HP electric, and spikes could be placed.
While I don't think Mega Beedrill will be a clearly present threat in the metagame it is worth talking about it too. First things first, yes, it's shit. But the thing is is that the main competitor for poor ol' Barry is now gone. Beedrill is now the fastest voltturner in the metagame, which gives it a small but deserved niche. Unlike Pheromosa, it will have a lot of trouble muscling past its checks and counters, and will by no means be a replacement, at least now there is some small but reason to use it beyond the reason of "lol memes."
Two more Pokemon that I believe will be hit hard by the nerf are Alolan Marowak and Toxapex. Alolan Marowak I won't cover, because above Ema Skye has made a short but detailed post that could sum up anything I could say in only two sentences. Although to add some light to the end of the tunnel, Alolawak is still viable as a stall breaker and trick room sweeper. Onto Toxapex, in my opinion it is a healthy nerf. The urchin no longer is a must on balance for one, and Toxapex offense is now quite possibly become just evidence of a lazy team builder.
Since we're past Toxapex offense, I'd like to move onto what I find to be the most notable buff/nerf with the Pheromosa ban. Hyper offense is now a lot more viable. Firstly, HO no longer has to use Pheromosa itself as a first, freeing up a sixth slot for a team that might need it. But the most important thing is is that the playstyle no longer has to sack one Pokemon to get in a Pokemon with a priority move that might not even kill the thing! That isn't even to mention the restrictions it used to put on teambuilding are now gone, not just for HO but for all playstyles.