Flygon D -> Unranked
Flygon doesn't really have a niche that isn't outclassed by another Pokemon or just not worth it. Garchomp outclasses the scarf set, it is pretty frail, it is pretty weak without a Band, and then it gets outsped by most megas and easily revenge killed.
Flygon's only notable niches are U-Turn and Defog. U-Turn isn't really worth the power drop from Garchomp, and there are better ground types that can use Choice Scarf and U-Turn. And there are better defoggers than Flygon, like Lati@s, Skarmory, and Mew.
How the hell did Flygon even get ranked anyway? Its damage output is shit, it's not even good at Defogging, it's not bulky, its damage output is shit, and... Why would you
use this thing over
anything in
literally anything it can do? This isn't DPP, don't use Flygon. Scarf sets are outclassed by Garchomp, Band sets are outclassed by anything that can use a Choice Band, Defog sets are outclassed by basically every Defogger.... Yeah, no reason to use this thing. At least Zygarde is decent enough for people who want to use a Dragon/Ground type but think Garchomp is too mainstream... Flygon is just shit.
Just... How did this get ranked in the first place?
Flygon is very rank, and so we need to
unrank it.
Here's a gun so you can shoot me for saying that.
Eh, I feel like you guys didn't read the nomination post at all...I never mentioned anything about Scarf or Band or whatever Flygon. The main niche is its Defog set because of its amazing typing and ability (with all hazards up, it only takes 6% switching in), and its ability to beat the majority of "mid-game" (by this I mean, more longevity than a suicide lead) Stealth Rockers in the OU metagame 1v1; namely, Landorus-T, Ferrothorn, Heatran, Tyranitar, Jirachi, Empoleon, etc. Don't forget about it's ability to put the hurt on a lot of OU's Spikers as well, namely Klefki, Skarmory, and the aforementioned Ferrothorn, while taking comparatively little damage from each in return.
That being said, there are a few Stealth Rockers Flygon understandably can't beat. Clefable is the main one I've heard about, but I just wanted to say SR Clefable's utility has decreased quite a bit due to the prevalence of things such as Mega Sableye, which pretty much force it to run Calm Mind to keep up, or Unaware which generally needs the moveslots for Wish, Protect, Heal Bell, n' other stuff. Garchomp is another one, but Garchomp is a different case as it typically has very short longevity on the builds it's used on. The majority of builds that Garchomp is used on treat it as a suidice Rocker, meaning that it ususally sacrifices itself to get rocks, or doesn't hang around for more than a few turns after it gets Rocks.
Finally, Flygon's role isn't limited to just Defogging, it can serve as a utility check to things such as Excadrill and Mega Scizor.
If you need specifics:
This is what I would call the "optimal" set for Flygon to serve its purpose (of course, it can definitely afford to drop a little more speed if necessary)
Flygon @ Leftovers
Levitate | 208 HP / 148 Def / 152 Spe | Naive
Earthquake | Defog | Roost | Fire Blast
Overall, obviously not the best Pokemon in OU by any means, but a neat hazard control 'Mon that carves a small niche out for itself, imo.
And just a note, a bulkier spread of 208 HP / 240 Def / 60 Spe Naive can be considered if the extra speed isn't needed (admittedly, it really isn't a lot of the time) and it helps Flygon check stuff like Mega Metagross, Beedrill, and Kabutops a bit better (Jolly Meteor Mash only has a 13.3% chance to 2HKO after Leftovers, while Flygon 2HKOs in return IIRC. Also it has a very good chance of living a 252+ LO Kabutops Stone Edge followed by Rain Waterfall after Leftovers, while OHKOing with EQ in return after 2 rounds of LO damage - two unlikely scenarios, but felt that they were worth pointing out.)
But yeah, overall, remember I'm not advocating for the new like S-rank 'Mon or anything, it's D-rank, which means it has a tiny niche, and I think that's exactly what Flygon is in ORAS.
also thanks to .cuteuser ben gay for letting me know, didn't get a notif that the bae flygon was bein' attacked n' such for some reason, heartless users man gosh *-*