That was a fun read...
I'd like to nominate
Excadrill B to B+. Excadrill is a great mon to use for a number of reasons and I was surprised to see it ranked below Rotom-W, Keldeo, M-Venusaur and M-Sableye, but rather alongside Reuniclus and Gastrodon. The reason I think Excadrill is better than this is because it has a number of roles that it performs very effectively; whereas these mons all have only one they do well or possibly two roles that they fulfill decently, like M-Sableye only being viable on stall, or Keldeo being a decent Scarfer and stallbreaker.
Excadrill is an awesome Suicide lead thanks to Mold Breaker preventing Magic Bounce, as well as an OK speed tier with great attack and good typing, with Rapid Spin. It can do work against a lot of common setters/leads in the tier right now. Toxic Def Lando/Spin Rocks away, OHKO Heatran, Toxic and set vs Sableye, OHKO Diance, does like 80% to Pex. It also puts in work against some defoggers too, Zapdos hates Toxic, Rotom-W takes like 85% from EQ and Latios 75%. This may not seem 'amazing' but remember this is a B rank
suicide lead doing all this work, yes I know Lando is better, but there is a reason he is S rank and also he doesn't have Mold Breaker, which is more than good niche, you can also kill Mimikyu through Disguise, so thats nice.
Hippowdon is rising up lately so we now have two very good, reliable sand setters with this and Tyranitar. Sand Rush Excadrill is excellent, Life Orb and Swords Dance allows this thing to hit so goddamn hard and its backed up by 604 speed in sand, outspeeding the entire meta. The main reason to use this right now has got to be vs KokoLucha, you can set up in the face of Koko, as it cannot 2HKO you no matter what set and Hawlucha goes down to a +2 Iron Head, obviously you outspeed them both in Sand. Revenge killing Koko, Volcarona, SG Magearna, Lele, Kyurem-B, M-Lopunny, M-Medicham, M-Mawile, M-Pinsir and on and on is amazing (a few require some hazard chip, but luckily this is very easy with Sand). Its also is a great hazard clearer, being immune to Toxic and resistant to Rocks, as well as having the advantage over Defog of leaving hazards on your opponents side. It can also use Z-Crystals to break past bulky checks in conjunction with Iron Head or Rock Slide, this also pairs great with Lele to avoid priority and Lele can bust down physical walls that can get in the way of a sweep. Without sand you still outspeed max speed Heatran and Mamoswine which is nice, two more threats which are very prominent as of late.
Choice Scarf is actually also pretty good to revenge kill and late game sweep. Its similar to Sand Rush but having access to Mold Breaker is nice and obviously its speed isn't reliant on Sand, this is definitely its worst set, not revenging +1 Volc, but its definitely not the worst option I've seen for Scarf with great Attack and STAB. A lot of the good things about this set have already been covered above.
There's a lot of things I haven't gone over. Although I feel that Excadrill was underrated in B anyway; recent trends like KokoLucha and the rise of Hippowdon make this thing a B+ rank threat, mainly for the first two sets I talked about.