One Pokemon I think has kinda slipped under the radar is Zygarde. Ever since the Power Construct ban, I've barely seen it at all, which is a shame because both formes are really good in their own ways.
10% is pretty one-dimensional and can barely switch into anything, but a lot of offensively-inclined teams just cannot handle it at all becuase of its speed tier combined with 1K arrows hitting everything that isn't a Grass or Bug type neutrally. Right now, it's having a hard time truly shining becuase the amount of ridiculously fast stuff in the tier makes 115 seem almost sluggish by comparaison (it does get ESpeed but doesn't really like getting locked into it that much). Tapu Bulu is also a massive, massive pain for it since it needs to play around it a lot, and even if it correctly predicts the switch-in, you still have to overcome Iron tail's horrid accuracy. But the many teams that rely on stuff like Celesteela, Rotom-W and RH Lando-T (which still takes 1K arrows well, but is usually oulasted by Zygarde since it can't inflict RH recoil) to take Ground moves have massive trouble vs this thing.
But as much as I love 10%, I think 50% is probably the bigger threat here. DD sets up very easily thanks to the bulk and hits the vast majority of the tier with a single move, making it a superb lategame sweeper, and a decent offensive glue for teams weak to stuff like Sand Rush Excadrill and Marowak.
The first set I used on it was DD / 1K Arrows / ESpeed / Outrage with a Lum Berry, but I wasn't quite satisfied with its damage output. Plus, I've actually found Outrage to be entirely pointless on the DD set since the only thing it really hits is Buzzwole, and I guess Pinsir, though you're better off running Rock coverage if you really want to hit Pinsir. Iron Tail is basically better since it hits Tapu Bulu which is, one again, a hard stop. But I usually find Sub to be the best choice, since Zygarde's bulk enables its sub to live some weaker hits (for instance, Amoonguss can't break it without Foul Play), and it lets you set up on status users without needing Lum, which lets you run another item.
Leftovers seems like the obvious choice for Sub sets, but i've actually been very pleased with Groundium-Z, which really increases Zygarde's power by giving it the ability to break past stuff like Tapu Fini and Clefable much more easily, and once that's gone, to just clean the rest of the team. It also weakens opposing Knock Offs which is nice. Sub+Groundium-Z gives you a pretty good middle ground bewteen Lum's Status resistance and Life Orb's breaking capabilitues. Unfortunately, Tectonic Rage from 1K Arrows doesn't hit flyers, so Earth Plate might be a pretty solid option too, for that reason.
Life Orb obviously doesn't mesh well with Substitute, so you'r better off running coverage. And although it might seem crazy, Sludge Wave, even with a -SpA nature, sounds like a viable option on it: it barely OHKOes 0/0 Tapu Bulu from full (and unlike Iron Tail, can't miss), and it 2HKOes Rocky Helmet Tangrowth. Of course, it doesn't deal much to Pinsir, and can't break Buzzzwole (nothing short of HP Flying can) so it's probably just a gimmick. Still, it's something to keep in mind.
All of this isn't even going into the SubCoil set, which seems like another very good bulky wincon even without Power Construct. I've actually been playing around with a Vincune-inspired Sub Protect Coil set with max Speed and it is very fun; it's not as good as Vincune since it's quite vulnerable on the special side and has more common and exploitable weaknesses, but it can still be extremely annoying to handle. You do probably want enough speed for Tapu Bulu though: as nice as Espeed is, Coil increasing the accuracy of Iron Tail so that you can reliably hit Bulu sounds really appealing to me.
So yeah, Zygarde is one hell of a threat, and more people should be using it.
