Okay then, I have some noteworthy nominations for the viability thread.
Kyurem-Black >Tier 1
Kyurem Black is easily one of the best Pokemon in my humble opinion. It provides powerful coverage and serves as a fantastic answer to teams that are reliant on abilities, especially type immunity ones.
Serperior > Tier 2
Contrary serves as a great counter to Intimidate for the team, with Serperior also being a capable Pokemon on its own.
Mega Camerupt > Tier 3
Don't get me wrong, it is a powerful Pokemon, but it only fits on Trick Room team.
Suicune > Tier 3
Having Inner Focus is nice, but I don't think Suicune deserve the Tier 2 spot with its lackluster firepower.
Arcanine > UR
Is there really any reason to use it over Incineroar? Incineroar provides utility options to the team such as Fake Out and Knock Off that Arcanine does not.
Mega Sceptile > UR
Having Lightning Rod sounds good in theory, but Mega Sceptile having too many type weaknesses mean it will fall flat in practice.
Mega Alakazam > UR
I don't see any point of using Mega Alakazam when Deoxys is available, who don't take a mega slot and having access to more appealing attacks. Might have been for Trace, but randomly copies a foe's ability makes it impractical.
I might update if I come up with a concrete reason for other Pokemon.
Agreeing with what HeatEdgeSword said, I think Serperior and Kyurem-B shoud rise to Tier 2 and Tier 1 respectively.
Kyurem-B has very powerful stats in general, having a very solid bulk and a decent speed tier, outpassing threats like the Oricorios, Kommo-o, Heatran and Lando-T (If not scarf) and speed tying with Tapu Lele and Zygarde. It also has the power to wallbreak through a decent number of teams, at the same time helping allies with a very useful coverage in Ice Beam, Fusion Bolt, Earth Power and Roost. It can pressure cores and teams that rely on inmunity abilities and others like Unaware Fable, fitting very well in almost any team (I've especially tried it in Rain Teams to break through Gastro's Storm Drain and it actually works very well).
And Serperior I think is one of the best support mons on the meta.It has a very great speed tier outpassing the 110 frontier and it's ability can be really useful if partnered with mons like Victini, Mega Manectric or decreasing stats moves in general. Serperior, as HeatEdgeSword said, can abuse opposite Intimidate to boost physical allies, also having acces to Glare, that can cripple opposite pokemon that rely on their speed tier like almost every offensive mon in the meta (except for slow wallbreakers and Trick Room abusers), and Taunt, that can be a headache to teams that rely on utility moves like Dancer Teams or TR Teams.
I'm not very fan about Mega-Camerupt falling to Tier 3, though. Even if it only works in Trick Room, TR is currently one of the best playstiles in this meta, potentially for Gastrodon and Mega-Camerupt. Actually, it got a 8,7% / 11,52% / 23,6% / 35,4% usage in 1000 / 1500 / 1630 / 1750 elo respectively this month (even if I don't really understand how because I remember that the best players where around 1520 elo, but meh, official stats are official stats after all).