After laddering for a few days here are my thoughts on a few mons:
- Mega Alakazam: Y'all are failing the people by not having Mega Zam as an S rank. It's the best offensive mon in the meta due to having limited checks. It's primary check is almost mandatory because it's on every team, and without A-Muk teams get 6-0'd. Truly threatening.
- Mega Charizard X: Poor zard. It just can't catch a break. It has nearly everything a mon could want in this meta, with good typing for the meta, solid bulk, a good speed tier, and potential to break. Then they gave us permanent stealth rocks. Top of B is probably about the right place for it, as it can still come in at 50% (after rocks) and roost on things like muk.
- Gengar: Mega is outclassed by zam as a purely offensive mon, but it does have a niche with access to wisp. Regular Gengar is a terror to deal with on Mega zam+Gengar offensive cores. They share checks, but their checks don't have reliable recovery. I would probably move it to A.
- MelMetal: As JTD783 said: It's very strong, particularly with t-wave. My zard X team has been running fire blast just to ohko it. It has some solid checks, but has coverage for them and 135 hp makes it hard to take out, even for special attackers.
- Eevee: It's been said before, but all of its moves are ridiculous. Having access to the only reliable way to remove status alone will keep it S for the forseeable future.
- Kabutops: Probably shouldn't be unranked. It has a niche in beating all of the common lead stealth rockers. Priority Aqua Jet is useful in a metagame where zapdos is strong (and therefore so are its checks) and mega zam/mega aero are running through teams. Far from top tier, but probably more consistent than all of lower C and half of upper C.
- A-Muk: Mandatory unless you want to lose to Mega Zam or Mega Gengar. Also functions as a soft zapdos check.
- Rhydon: Good because of Zapdos and Muk being so common.
- Mew: Does everything. Also S for the forseeable future.