Hey guys, I just thought I'd give you my ranking - obviously here there's a degree of personal preference.
Ttar-rank
Tyranitar - this guy is honestly a step up from anyone else in the whole tier. So versatile, so powerful, a huge game-changer. If you don't have this guy in your team, you already have a small disadvantage before the battle starts. His DD set is just amazing and one of the lategame's best mons, his CB set hits like a truck, and his Pursuit set single-handedly makes Forretress viable. He also brings sand to the table which is a valuable asset against things like Cune and Curselax. I think that while being a step above everyone he's also very good for the meta, as otherwise ADV would be much slower and less interactive.
A-rank
As opposed to ordering my mons 1 by 1, I'm gonna break them into blocks of guys who are on a par with each other - the differences in viability are too marginal, and often you're comparing one thing with something very different.
A+
Skarmory - by far the best Spiker, amazing defense and utility mon. Unlike Forry, he actually checks things and can't be set up on as he can phaze.
Gengar - like Ttar, he's powerful and versatile. People think of him primarily to block spin, but he can only block Forry's and Cloy's spin, as he loses to Starmie and Claydol. His real strength is his status with Wisp and Hypnosis (the former can single-handedly neuter physical offense) and ability to pop guys like Bliss with a boom. He has a great ablilty in Levitate, allowing him to get in on guys like Flygon. Gar is a very dangerous mon.
Suicune - I changed my mind on this one, partially due to the communal disapproval at my previous ranking of him. The offensive set is super strong, especially with the right support (i.e. on a CM spam team), and the defensive set is very powerful late-game. That being said, I think Cune's hurt by Spikes and Sand a lot and is not as good at switching in as he's made out to be, which is why he's not number 2.
Snorlax - This is maybe a controversial one, but I think Lax is well up here. I think Curselax on its own is low B tier, but the reason this guy is up here is the boom. This guy played right will always trade 1 for 1, sometimes 2 for 1. A utility Lax is one of the best mons early game to set up for a strong lategame. He also checks quite a few special attackers and can keep them at bay while you set up for your own big guns to come out.
A
Heracross - so underrated it's criminal. You build around this guy, he'll win you games. With SD, a Sub and a Salac Berry, he's one of the few true sweepers. He can play wallbreaker too with Focus Punch - ever since Skarms stopped running Drill Peck/HP Flying, FPunch became super strong on SD Lefties Hera. Warning though, this guy does need considerable support to be used at his full potential.
Celebi - not as good as before. Can't stand up to Spikes, Sand, and Dug everywhere and new stuff like HP Bug Aero. That being said, still great with Leech Seed, or with the offensive CM set on the right kind of team.
Swampert - keeps a LOT of mons in check. Sticks around for a long time as long as he doesn't get poisoned, and dishes out his own poison too. Very solid pick, and also hidden OP on the right teams with Endeavor.
Aerodactyl - fast, powerful, the cleanup crew. When the fighting draws to a close, the buzzards swoop down for the bodies. Fast as Sonic and Usain Bolt's lovechild, this guy's the finisher.
Metagross - like Lax, all about the boom. This guy pops early and takes a big fat tank down with him, and suddenly the opposing team looks a lot weaker. A godsend for physical offense teams.
A-
Zapdos - the bird can Sleep Talk and phaze, or it can hit hard and keep momentum with BP. Modest Zap hits hard, but offensive Zaps are stopped cold by Blissey.
Dugtrio - traps quite a number of mons and opens up holes that can be exploited by all sorts of teams, most often CM spam or stall. Also outspeeds +1 DDtar - shame Jolly can't oneshot a full health dino with the right EVs. I actually prefer Adamant to Jolly on a lot of my Dugs, unless i'm really scared of Kou.
Blissey - I don't like to use her myself, but I hate to play against her too. She keeps a lot of mons in check, and plays best on a slow team with Spikes. CM is a nice set, but it's a shame you lose out on a little bulk and SToss and Toxic there.
Magneton - this guy's clutch as fuck, and his trapping ability on Skarm pretty much makes physical hyper offense viable. Traps Forry too, which is sweet.
Flygon - relevant as ever, very hard to switch into with Spikes and Sand support, and also not vulnerable to either of them. Great vs DDtar. The 4x Ice weak is probably what holds it back most.
Jirachi - better on paper than in practice - he wins a lot of 1v1s, but at times he can be a momentum loser - also trapped by Dug which is annoying. Superachi is fun and powerful.
B-rank
B+
Salamence - some people won't like him this low, but who can honestly say that DDmence strikes fear into them? CBmence, Elemence, and Wishmence are better sets than DD (Elemence is the best imo), but unfortunately DD's the one that's most often used.
Starmie - spins but does nothing else. If your team doesn't like spikes, then this guy will always get his spin off. Unfortunately he poses no other threat, as things like Bliss laugh at him.
Forretress - the second Spiker. Notable for having spin, but is a poor user as it has no built-in ability to beat Gar. Explosion is nice but weaker than other booms. Earthquake is great for Mag, and HP Fire is nice for mirror matches. Unfortunately, this guy has chronic 4MSS.
Porygon2 - this guy's both the anti-Dugtrio measure, and a defensive pivot in his own right. Not as Toxic weak as would seem with his ability to trace Natural Cure, but doesn't take too kindly to Spikes and Sand.
B
Raikou - I know some people rate him higher, but his issue is that he needs a lot of support - he's a high-maintenace mon. I put Hera, another high-maintenance mon, far higher up the list as he brings far better results in practice, and is more flexible than Kou as well - Kou only fits on one specific kind of team.
Gyarados - can do well in the right conditions - his typing is very good, but it's a shame that he gets so hard-walled by the untrappable and hard-to-bait Zapdos. Double-Edge is poor as it means you have to forgo Taunt, which means you actually lose to the Toxic-carrying Waters you once set up on. Also absolutely REQUIRES Mag, as he'lll do nothing otherwise. RestTalk is fun on the right kind of team.
Jolteon - fast like Ramadan, good for keeping up momentum with BP, but too squishy and weak to the elements to last until late, and too easily walled to punch holes early. Can be good roaring with spikes in midgame though.
Claydol - spins too, not quite as reliably as Starmie. Even more dead weight than Star and probably less durable too due to lack of Natural Cure. Counters Taunt DDtar hard, which is nice.
B-
Cloyster - the third Spiker. Not durable like Skarm and Forry, but has better boom targets and can hurt Gar somewhat with Surfs. You probably won't get to Spin with it - this guy sets up Spikes and goes pop.
Regice - better on paper than in practice. Would be really good if it had a better Attack stat - booms and Focus Punches are still really weak with a lot of EVs, and having these moves mean that less EVs can go towards Special Attack. Defensive Ice is too weak to the elements to last long. Use Blissey instead for special walling purposes.
Houndoom - the other pursuiter, used when you don't want sand, i.e. you have a Curselax. Has Wisp and is slightly more specially powerful and fast than Tar, but is painfully squishy and fails to do its job more often than Tar. Often the no sand thing backfires too as they probably have a Tar.
Medicham - very hard to use but very powerful. High risk, high reward.
Vaporeon - not used it much myself but I know a lot of good ADVers got a soft spot for this guy.
Slaking - this guy fell hugely out of favour but is still strong when used right IMO. He's a hard-to-play mon, but the returns are great if you predict well.
Charizard - this guy hits ridiculously hard. Requires some decent team support but can do some serious damage if you pet him right. Has the potential to do nothing sometimes though, not very consistent.