Update to Version 1.3:
So, there have been discussions going on about what to do with this thread, and this update will be the first step in enacting them. Primarily, there will be a heavy stress placed upon actual finishes at events when it comes to determining rank, and theorying will be minimized. Beyond that, the list is going to be trimmed, a lot, simply to remove things that are kinda meh. Should the find their place in the metagame they'll be added back in, but until they do they'll exist in a sort of unranked zone. Allow me to further clarify:
As one example, Conkeldurr's getting cut from these rankings entirely. That doesn't mean it's a bad Pokemon, it just means that nobody's done anything notable with it yet. Working with what could theoretically be good is cool and all, but it's just not feasible. Now, both Cherim and Golduck will be getting dropped to D Rank. This does not mean that they are better than the unranked Conkeldurr; they will be placed in D rank because they're prefect examples of gimmicky Pokemon that you might think are good but really aren't. With that hopefully cleared up, let's start:
Kyurem-W, Mewtwo, Conkeldurr, Hariyama, Clefairy, Clefable, Goodra, Mega-Mewtwo-X, Mega-Mewtwo-Y, Porygon2, Parasect, Venusaur, Hydreigon, Kingdra, Kyogre (regular), Groudon (regular), Machamp, Mega-Houndoom, Mega-Camerupt, Chansey, Dusclops, Gardevoir, Blissey, Rotom-W, Kyurem-B, Reshiram, Mega-Venusaur, Mega-Blaziken, Tyranitar (regular), Volcarona, Scrafty, Bisharp, Hitmontop, Heatran, Azumarill, Swampert, Virizion, Lugia Krookodile, Latias, Zekrom, Porygon-Z, Rhydon, Rhyperior, Rotom-C, Mega-Manectric, Rotom-F, Giratina-A, Metagross (regular), Sylveon, Staraptor, Sableye Mega-Metagross, Mega-Lucario Rotom-H and the entirety of the current D rank bar Mega-Scizor unranked
Yeah, lots of cuts. Still, look at everything on this list. To the best of my knowledge, Cherim has done better than them (it's cut a Regional, sadly enough) so until they do something they're off the list.
Cresselia to A
This is a pretty simple change, nothing major. As pointed out, power creep has definately hindered Cress and while it's still certainly good it's just not A+ material.
Golduck and Cherim to D Rank
Do I really need to explain this? They shouldn't have ever been in the C's.
Gothitelle to C
It actually cut an event, what do you know? It has a cool ability and decent bulk with a nice support movepool to back it up, but all the same it goes down too quickly and if you really want support then there's always Cress/Smeargle.
Mega-Rayquaza and Rayquaza are now slashed in A rank
It's been suggested several times, and because Rayquaza doesn't actually need a Mega Stone to Mega evolve you can have a Semi-Mega Rayquaza pretty easily. This could be changed in the future depending on some things (I mean, Rayquaza and Mega-Ray often run different sets with regular Ray sometimes opting for Waterfall and Overheat with little intention to Mega-Evolve), but if it's an issue we can have a more complete discussion about it.
Landorus-T back to A-
It's Landorus, and it seems that it's reign isn't over yet.
Dialga and Giratina-O to B+
Both are pretty good, but not really A class threats. You should watch out for them in teambuilding, but they each struggle with at least one of the S Class Pokemon and some of the higher A class Pokemon.
Landorus-I dropped to C+
This thing hasn't done much at all at live events, and the only reason it hasn't gotten the sack yet is because it can kinda beat Primal Groudon. With that said, it Landorus-I continues to achieve nothing, it won't stick around on the rankings for much longer.
Togekiss to A-
In competition for the best redirection user in the format with Amoonguss (and Smeargle I guess), Togekiss deserves it's spot in the A rank. More than redirection, it's also a great source of speed control and actually has amazing bulk, to the point where it can take a +2 Xerneas Moonblast if EVed correctly.
Aegislash to B
Without a single high event placing to my knowledge, Aegislash is losing ground. It's still a good Wide Guard user, but it can't hold on forever without a decent finish. I'm waiting to see how this one pans out.
Latios to B
It's decent and has nice support options. Because of a lack of event finishes it won't go higher, but B seems like a nice enough home for it right now.
Mega-Swampert to C
Same old, same old. No event finishes, generally eh overall.
Ludicolo to C+
Ludicolo doesn't have any awesome finishes, but it's around in the meta so it gets to stay for the moment.
Smeargle to A+
Dark Void
Liepard to A-
More event finish issues/corrections
Palkia, Mega-Lopunny and Weavile to B
They've been used, they're okay, but they're not amazing
Klefki to B-
Jon Hu
Gengar (regular) added to B-
It's won a Regional, but nothing much besides that. It might move up or down depending on how the rest of the season plays out for it.
Togetec. . . Togetech. . . Togenotkissthingy added to C+
Yeah, this seems like a horrible theorymon or a plain badmon, but it did win a Regional. Doesn't exactly make it good, but then again C+ is a relatively humble place to start. I'm tentatively optimistic that Togenotkissthingy can prove to be a viable Pokemon in VGC '16.
Raichu added to B+
Say what? Well, Raichu has actually been doing way better than you'd think at events, having won a Regional already and shown up in Top Cut several times besides that.
S Rank collapsed into one tier
I'll probably follow this up with an update early next week (or whenever we get another page or two) to run damage control and begin to flesh the thread back out. From here on, please cite successes that any nom you've made (to be added) has seen.