Since the meta isn't very big right now, 99% of my matches are just M'joe'ra and I facing off, countering each other's teams and such. We continuously make new teams and strategies, so I figured I'd point out a few threats that remain true through all of our matches. Tail Glow + Surf Manaphy is definitely a constant threat to many teams, as it hits even resists, which are rather scarce I might add, with insane power. It's speed and power were such problems for my first drafts of teams that I opted to create a set to hard counter it. This is when Unaware Clefable was born, but even that gets 3HKO'd if you don't link Cosmic Power and Moonlight. It soon became clear, however, that Clef can be useful for many pokes other than Manaphy too. This makes it another prominent threat that's arguably a must have for every team, as any type of setting up, weather offensive or defensive, is stopped dead in its tracks by this monster. The low Moonlight PP is sometimes a problem, but it can run Rocky Helmet rather effectively to punish those who try to hurt it.
Another extremely valuable poke for a team is Magnezone. The discovery of this Pokemon's uses in Linked goes all to M'joe'ra, and he's made more than one successful set with him as the platform. The original idea was Analytic Sub + Thunderbolt, which had massive damage output and was incredibly difficult to break once Sub was up. After this became predictable, another threat arose, namely Mega Diance. Because of this, Mjoe stuck a Scarf on Zone, seeing that it just barely outspeeds full speed EV Mega Diance. He then linked Thunderbolt + Flash Cannon, which hits most of the metagame with neutral/SE damage, and also OHKO's Diance. Surprisingly, this double STAB combo was more difficult for me to adapt to than even Tail Glow Manaphy in some ways, and it's speed is really obnoxious. Speaking of Mega Diance though, it can also run a very formidable set involving double STAB via Diamond Storm + Moonblast. It's great speed tier paired with Magic Bounce to counter any Prankster shenanigans make for a threatening force that hits really hard. I always make sure to have at least one Steel move, just in case.
Dragon Dance Altaria is pretty good too, but it doesn't seem to sweep my teams anymore. I think it's best claim to fame is that it does ~60% to Unaware Clef, making a switch-in impossible, which is something Manaphy cannot achieve.