This is finally open again and I can talk about a common mons which I think are interesting to use with the right support:
With balance teams seeing more usage, Gastrodon has been a cool pick to use with things like Celesteela, Landorus, and so on due to their amazing synergy. Gastrodon [usually] stops most common special attackers like Koko, Magearna, Latios (bar Trick), Greninja, Diancie, Keldeo, Zapdos, Zam, etc which can be very helpful for a lot of teams. Its amazing typing means that it's only weak to the few Grass types that are in the tier. Although it still struggles with TSpikes being everywhere, it still scares the likes of Toxapex when they're not on and is also not completely passive due to its wonderful ability. Definitely more of a situtational, niche pick, but I think it can still be quite good with the proper team support. I'll include a couple replays showcasing it:
Vertex vs Cdumas
Short replay, but effective at showing how good of a mu Gastrodon has vs. rain. Vertex's main way of breaking through Gastro was Kartana, but with a Celesteela in the back, Vertex was forced to play aggressively and try to circumnavigate this. Cdumas's TSpike early on helped, since all the possible mons that could pressure Celesteela were put on a timer early. If the game would've continued, Cdumas had Gastro to continuously check Koko, one of the only real threats to Celesteela. Having Kartana in the back also helped apply a lot of pressure. Although it was a short match, it still shows how potent a Gastro core can be.
Ricardo vs Tricking
From preview, we see that Tricking has a few ways to compromise Gastro: Toxic/Taunt from Alo/Tran, Trick from Latios, and physical attacks from Lando/Lop. Ricardo's Tran goes down early on but he's able to bounce back by picking Lando off with his own CC. Although Latios could click Trick against Gastro on the potential switch, it has to watch out vs the possible switch to something else. Gastro is able to shrug off a Draco with ease, and then Ricardo puts Alo on a timer with synchronize Toxic. Gastro toxics Latios, which means that one of the biggest ways of crippling Gastro is now also put on a timer. Latios is also forced to stay relatively healthy and prevent a lot of hazard from going up. After a series of events occur, Gastro ends up Toxic'd and Latios ends up tricking Mew. This allows Gastro to continuously keep switching in throughout the battle, even while status'd, vs Alomomola, Mage, and Latios. This replay shows that although Tricking had ways of dealing with Gastrodon, Ricardo was able to make the right plays throughout the battle and slowly eliminate Tricking's ways of dealing with Gastro to a point where Gastro could easily wall and win with hazards up.
With all the hazard stacking that fills the meta, Reuniclus finds itself in a better spot than before, being able to avoid any sort of damage due to Magic Guard. With Mew falling off the radar, Reuniclus is a good pick as a bulky psychic that isn't as passive as Mew and can still counter a lot of physical attackers or setup on a lot of passive mons, as well as on the ever-popular Celesteela+Toxapex core. It really appreciates Toxapex and Ferro being all over the place right now, as it finds it relatively easy to set up a CM on these passive mons and proceed to threaten something with Psyshock / FB. Again, I grabbed a couple replays that I found to show that Reuniclus can be good pick given proper support.
Snou vs Ojama
Here, Ojama takes advantage of defensive Lando-T and Tangrowth to set up CM's early in the game. This forces Snou to sac something (in this case, Latios after a Trick) to cripple Reuniclus, even after a flinch. Unfortunately, Medi's HJK missed, but this replay still shows the pressure Reuni was able to exert early game, allowing hazards to be up and wear down Snou's team after Latios went down.
Bushtush vs Cdumas
Here, Bushtush has ways of dealing with Reuni in Heatran (situational) and Scizor, which turns out to be SD. Reuni is nicely supported by the likes of Lele and Toxapex, which can keep Scizor in check, especially after Heatran takes 3/4 of its health from TTar's Stone Edge. Although Reuni doesn't do anything outright, this game still shows how potent it is when paired alongside Toxapex. After Cdumas stacks hazards, he only needs to keep Toxapex healthy to counter Zor (hence probably why Bushtush didn't want to defog hazards) and on the flipside, Bushtush needs to keep Zor alive in order for Reuniclus to not set up and win against the rest of his team. With hazards on Bushtush's side, it's only a matter of time until he can keep switching in the rest of his mons, and due to having to keep Zor healthy for Reuni, ends up losing 1v1 at the end vs Toxapex.
Googly vs Sabella
Googly ends up using the same team from the previous replay while Sabella uses a Chansey balance squad. Chansey reveals TWave early on, which can neuter Reuni from reliably setting up and getting hits off. Pinsir, the yellow color, and Kart (if SD) can all beat Reuni given the right situation. Kartana wastes its Dark-Z on Lando-T, which potentially eliminates a problem for Reuni. After Sabella reveals Sub on Pinsir, Googly does a good job on eliminating Pinsir with Pursuit on TTar to remove another one of Reuni's problems. Sabella ends up CM'ing with Clef alongside Reuni and unfortunately ends up critting Moonblast to take it down. Had that not been the case, Reuni would've been able to easily clean up as even at +2, Kart is doing 33% max. Shows how good Reuniclus can be vs bulkier archetypes even with para, as it won without crit.
Overall, I think that with the proper team support, both Gastrodon and Reuniclus are cool picks in the meta that a lot of teams don't take into account besides common answers like Toxic / Taunt. I might be a bit biased with my love for BO teams, but I wanted to hear people's thoughts on both of these mons. There's obviously still things like TSpikes for Gastro and dark types / Taunt for Reuni, but I've been having a lot of success using them lately.