I'm just going to post my most recent nominations from the old forum:
Ok, here are my thoughts:
Chesnaught for B+/B
Chesnaught is such a good Pokemon this gen. It's Grass/Fighting typing is extremely helpful for defensive teams, as it allows him to resist the popular EdgeQuake combination. Leech Seed and Spiky Shield are also really great moves that can easily where down physical attackers. Synthesis provides reliable Recovery, and his ability, Bulletproof, allows Chesanught to wall Pokemon it would never normally wall before, such as Aegislash and Gengar. Overall, this thing's great typing, ability, and support movepool warrant B in my eyes, if not B+.
Next, I'd like to nominate Celebi for B-
Celebi is criminally under-rated this generation. While it's defensive set may face serious competition from Mega Venusaur, offensive Celebi is one of the best specially-offensive Grass-types in the tier. With access to STAB Leaf Storm and Psychic, as well as great coverage moves in Earth Power, Ancient power, and Hidden Power, Celebi can definitely do a lot of damage to the opponent's team. Combine this with the fact that it's one of the best Rotom-W counters in the game, and you have an great offensive Pokemon on your hands. Celebi's offensive set differentiates itself from Mega Venusaur by having more Speed, and more importantly, it doesn't take up a Mega slot, allowing you to run other potential Mega Evolutions such as Pinsir, Charizard, and Tyranitar.
I'd also like to nominate Thundurus-T for B-
Thundurus-T definitely faces a lot of competition from it's other Electric/Flying brethren, Zapdos and Thundurus. However, Thundurus-T differentiates itself by having a massive base 145 SpA, making it hit much harder than Thundurus. Thundurus-T's Dual Dance set is still very potent, even with the Hidden Power nerf, as it's large attack stat means it can still dish out a lot of damage. I've also used a Choice Scarf Thundurus on a Rain team of mine, and it's been doing surprisingly well, especially when in combination with other fast Pokemon such as Tornadus-T. All in all, while Thundurus-T has a lot of competition as an Electric/Flying type, it's niche is large enough to warrant B- in my eyes.
Finally, I'd like to nominate Vaporeon for C-/D
Vaporeon was a Pokemon who was in D rank last generation, and with things only getting worse for it, I see no reason for it to have risen. The Rain nerf hit Vaporeon the hardest, as it now cannot abuse the once usable Hydration + Rest combination. Even with this combination, it faces serious competition from Pokemon such as Manaphy and Goodra for a spot as a Hydration Rest user. It also finds its role as a bulky-water type heavily outclassed by Quagsire on stall, who with access to Unaware makes it a much better option. All I can really see Vaporeon doing in OU is Baton Pass, which even then leaves it at a very low rank in my eyes.
Also, I haven't had enough experience with it, but does Krookodile really warrant C+ status? It faces heavy competition for a bulky-Ground type by Landorus-T, Hippowdon, Gliscor, and to a lesser extent Quagsire and Gastrodon, all of which have access to much better bulk. All I can really see Krookodile doing is using it's Dark-typing to help absorb certain blows and it's access to Knock Off, but even then I feel like this thing would be perfectly fine in C.
EDIT: Just noticed Gothitelle is unranked ATM. This thing definitely deserves B-, due to it's amazing trapping skills. Especially against stall, if Gothitelle can switch in on the right Pokemon (Which usually will happen with smart double switching) then it can completely eliminate the Pokemon, which in turn can destroy cores. I do find this thing to be a dead weight a lot of the time against offense, however, but it's positive traits against stall really make it worthy of B-.