Chinchou: I think D-tier is fine. Stats have always been Chinchou's main issue, but it ticks the boxes in most of the other categories. Unfortunate that the next gym after getting it is probably its worst one, but there are others where it does much better.
Chingling: Agree with E-tier. My only experience with this is from a Diamond playthrough. It was awful. I don't think much has changed to make it better. At least it comes early with at least 3 31 IVs and a favourable match-up coming up...
Cubone: I think it's worth noting that Cubone has a 20% chance of holding Thick Club if you lead with something with Compound Eyes (Nincada is readily available as a Compound Eyes slave, but Vivillon and Butterfree also work). Those odds aren't actually that bad. However, I'm not sure if that's good enough because that still means an 80% chance of missing out, plus you have to encounter a Cubone in an area where lots of other Pokemon are found, so that odds are still a bit too low for an efficient run. If we don't have a problem with this then it should definitely be at least C-tier, or possibly even B. If not, D-tier seems fine for it since it's fairly weak without its signature item, and it's slow on top of that, but it's movepool is decent - STAB Bonemerang at level 21 is cool and Rock Tomb is handy also.
Dedenne: E-tier definitely. Not even sure how beneficial making it part Fairy was to it...
Electrike/Houndour: Doing these together since they basically have the same strengths and weaknesses. While I do think that learning only physical moves early on is unfortunate, the fact that they evolve early does make up for it somewhat. Houndoom gets 90 Attack at level 24, so is can use things like Fire Fang, Bite and Feint Attack somewhat well until its special moves come along late-game. Admittedly its first gym battles aren't good for it, but it gets several decent to good match-ups later on. C-tier would be fine for Houndour I think. Electrike is similar. It evolves just a bit later, but it is significantly weaker in Attack. On the plus side, it doesn't have to wait as long for a special move since Thunderbolt is much earlier than Flamethrower or Dark Pulse. Manectric itself gets Flamethrower too, which is fairly niche for an Electric-type. I think C-tier would be ok for Electrike too.
Exeggcute: Could go either way. It has high attacking stats but pretty much nothing to use them with for a while: Confusion and Grass Knot, that's it. Plus it's slow and lacking in special bulk, and it isn't exactly setting the world on fire with its match-ups either. Wood Hammer at level 37 is ok though (I think that would be around the 5th gym depending on team size, recoil sucks though) and its late-game options are much better. I prefer to be conservative in cases that I view as borderline so I'd probably go E-tier, but I don't really feel that confident in saying that.
Ferroseed: I also agree with what others have said about D being too low. I think this looks pretty similar to Steelix; what it lacks in raw power and Speed it makes up for in resistances and bulk. I'll go with C-tier just to be conservative, but B-tier is ok too if more people want that instead.
Gorebyss/Huntail: Gorebyss is definitely better, but I'm not really sure that Huntail is so much worse than Gorebyss that it should end up in a lower tier. 94 Sp Atk isn't that bad and it's supported by 104 Atk. It looks like it could be an ok mixed attacker with Surf, Ice Beam, Waterfall, Ice Fang and Crunch to pick from across the game. If Gorebyss is going in D-tier I think Huntail should be too (or we could drop Gorebyss to E-tier, but either way I think they should be in the same tier).
Mantyke: Well Air Slash at level 36 isn't THAT late (although it does miss out on the Grass gym) and it gets Surf right away. Mantine looks similar to Lanturn in terms of raw power. It has a good Special movepool (Surf, Air Slash, Ice Beam, Psybeam and Signal Beam). Match-ups are ok, not great (most of the Elite 4 has a least 1 Electric move). I guess D-tier is ok, won't complain if it ends up in E instead. Catching it can be annoying though, since its catch-rate is surprisingly low.
Mareep: Between C and D, I'd pick D. I just think horde exclusives are mostly poor choices. This one happens to get a mega-evolution though, so I guess it is better than other horde Pokemon.
Mawile: I was about to make an argument for this in D-tier mostly because its typing would give it great match-ups against many important trainers. It's basically a bad Steelix. However, aside from its poor stats, its early-game movepool blows. Fairy Wind as its best STAB until you reach the move relearner is pretty bad, and Mawile isn't really strong enough to rely on unSTABed coverage moves for that long. So E-tier is probably best - its decent match-ups and early appearance are enough to keep it out of F-tier.
Nidorans: Yeah agree with B-tier for both. They've always been at least decent in any game they've appeared in (and ofter better than decent), and they got even better with the extra 10 points they got in Attack. I probably would stay away from Sheer Force though since you'd likely waste more time trying to get them than you would save by having it on your team.
Remoraid: D-tier is ok, don't have much to say about it.
Roggenrola: I'm curious as to whether a split entry would be justified here. Probably not, but getting a Gigalith at level 25 over Boldore would be particularly helpful against special attackers. But in any case it doesn't seem that useful. Rock by itself isn't that great, and you have maybe 2 favourable match-ups in exchange for poor ones against the first 2 gyms it faces and at least 2 of the Elite 4. Low Speed isn't helpful for routes, and it doesn't have a stack of resistances to help it out either, though its physical bulk is great. Movepool is basically limited to STAB + Earthquake, which isn't too bad but could be wider. Would probably go E just to be conservative, but I don't feel confident here either.
Sigilyph: I lean towards B-tier. It's obtained early and is immediately powerful, with great stats and strong STAB moves, and the first 2 gyms it faces are in its favour. It doesn't really have any favourable match-ups after that but it can still contribute against other gyms and remains useful as a fast and powerful route cleaner that doesn't really drop off. And having something to deal with the fighting trainers in Reflection Cave is handy in any case.
Slowbro/Slowking: I guess I could make a similar argument to Thick Club Cubone here and say that Compound Eyes give you a 20% chance of getting a King's Rock from Hariyama (or Hawlucha, but Hariyama is probably easier). That would give you a potentially instant evolution for Slowpoke, in which case I could see a case for at least D-tier for Slowking. However, if we decide that's too much of a bother than E-tier alongside Slowbro might be best. I couldn't stress enough just how bad Slowpoke is before it evolves, which pretty much kills spoils things for Slowbro.
Snubbull: D-tier is fine. I think C-tier would be a bit high because it's slow and kinda frail and has no STAB for a while. Maybe if it had retained its Normal typing it would be higher, but it didn't so no.
Solosis: Just want to point out that Duosion has identical Sp. Atk and Speed to Reuniclus, and it can hold Eviolite to help make up for its worse bulk. Therefore, late evolution isn't as bad for Solosis as it might seem at first, since its middle stage (obtained at Level 32) has comparable power to its final stage. It also gets Psyshock at level 25 for a powerful STAB. Could see a case for C-tier, but no higher than that since it doesn't have many favourable match-ups and it is SLOW.
Stunky: ugh why can't this learn Poison Jab by TM before it evolves? D-tier is probably fine but it has a few flaws, such as being weak initially and evolving a bit late into another Pokemon whose stats aren't that great. It has a few options for moves though: Thief from TM and Slash at level 22 is...ok. It can try a Toxic + Venoshock combo too. When it evolves, Poison Jab is immediately available to it for a good reliable STAB, and um...Flamethrower. It only has 1 weakness too, which means it can contribute against many gym leaders, etc. if not beat them outright.
Yanma: er yeah I was going to say something similar to Ondore about putting this in E-tier instead. Being horde only is bad enough, but just look at how terrible Yanma's movepool is early on. Aerial Ace off 65 Attack and Sonicboom are its best moves, and Uproar isn't really that good either. It evolves at level 33 and is finally able to learn Struggle Bug, but by then it 50 base power seems a bit underwhelming and you aren't getting much better than that until the move relearner. So maybe Yanmega has some use late-game which is enough to put it above F-tier, but I think that you have to put up with a lot prior to that, to the point where I'd say E-tier.
Chingling: Agree with E-tier. My only experience with this is from a Diamond playthrough. It was awful. I don't think much has changed to make it better. At least it comes early with at least 3 31 IVs and a favourable match-up coming up...
Cubone: I think it's worth noting that Cubone has a 20% chance of holding Thick Club if you lead with something with Compound Eyes (Nincada is readily available as a Compound Eyes slave, but Vivillon and Butterfree also work). Those odds aren't actually that bad. However, I'm not sure if that's good enough because that still means an 80% chance of missing out, plus you have to encounter a Cubone in an area where lots of other Pokemon are found, so that odds are still a bit too low for an efficient run. If we don't have a problem with this then it should definitely be at least C-tier, or possibly even B. If not, D-tier seems fine for it since it's fairly weak without its signature item, and it's slow on top of that, but it's movepool is decent - STAB Bonemerang at level 21 is cool and Rock Tomb is handy also.
Dedenne: E-tier definitely. Not even sure how beneficial making it part Fairy was to it...
Electrike/Houndour: Doing these together since they basically have the same strengths and weaknesses. While I do think that learning only physical moves early on is unfortunate, the fact that they evolve early does make up for it somewhat. Houndoom gets 90 Attack at level 24, so is can use things like Fire Fang, Bite and Feint Attack somewhat well until its special moves come along late-game. Admittedly its first gym battles aren't good for it, but it gets several decent to good match-ups later on. C-tier would be fine for Houndour I think. Electrike is similar. It evolves just a bit later, but it is significantly weaker in Attack. On the plus side, it doesn't have to wait as long for a special move since Thunderbolt is much earlier than Flamethrower or Dark Pulse. Manectric itself gets Flamethrower too, which is fairly niche for an Electric-type. I think C-tier would be ok for Electrike too.
Exeggcute: Could go either way. It has high attacking stats but pretty much nothing to use them with for a while: Confusion and Grass Knot, that's it. Plus it's slow and lacking in special bulk, and it isn't exactly setting the world on fire with its match-ups either. Wood Hammer at level 37 is ok though (I think that would be around the 5th gym depending on team size, recoil sucks though) and its late-game options are much better. I prefer to be conservative in cases that I view as borderline so I'd probably go E-tier, but I don't really feel that confident in saying that.
Ferroseed: I also agree with what others have said about D being too low. I think this looks pretty similar to Steelix; what it lacks in raw power and Speed it makes up for in resistances and bulk. I'll go with C-tier just to be conservative, but B-tier is ok too if more people want that instead.
Gorebyss/Huntail: Gorebyss is definitely better, but I'm not really sure that Huntail is so much worse than Gorebyss that it should end up in a lower tier. 94 Sp Atk isn't that bad and it's supported by 104 Atk. It looks like it could be an ok mixed attacker with Surf, Ice Beam, Waterfall, Ice Fang and Crunch to pick from across the game. If Gorebyss is going in D-tier I think Huntail should be too (or we could drop Gorebyss to E-tier, but either way I think they should be in the same tier).
Mantyke: Well Air Slash at level 36 isn't THAT late (although it does miss out on the Grass gym) and it gets Surf right away. Mantine looks similar to Lanturn in terms of raw power. It has a good Special movepool (Surf, Air Slash, Ice Beam, Psybeam and Signal Beam). Match-ups are ok, not great (most of the Elite 4 has a least 1 Electric move). I guess D-tier is ok, won't complain if it ends up in E instead. Catching it can be annoying though, since its catch-rate is surprisingly low.
Mareep: Between C and D, I'd pick D. I just think horde exclusives are mostly poor choices. This one happens to get a mega-evolution though, so I guess it is better than other horde Pokemon.
Mawile: I was about to make an argument for this in D-tier mostly because its typing would give it great match-ups against many important trainers. It's basically a bad Steelix. However, aside from its poor stats, its early-game movepool blows. Fairy Wind as its best STAB until you reach the move relearner is pretty bad, and Mawile isn't really strong enough to rely on unSTABed coverage moves for that long. So E-tier is probably best - its decent match-ups and early appearance are enough to keep it out of F-tier.
Nidorans: Yeah agree with B-tier for both. They've always been at least decent in any game they've appeared in (and ofter better than decent), and they got even better with the extra 10 points they got in Attack. I probably would stay away from Sheer Force though since you'd likely waste more time trying to get them than you would save by having it on your team.
Remoraid: D-tier is ok, don't have much to say about it.
Roggenrola: I'm curious as to whether a split entry would be justified here. Probably not, but getting a Gigalith at level 25 over Boldore would be particularly helpful against special attackers. But in any case it doesn't seem that useful. Rock by itself isn't that great, and you have maybe 2 favourable match-ups in exchange for poor ones against the first 2 gyms it faces and at least 2 of the Elite 4. Low Speed isn't helpful for routes, and it doesn't have a stack of resistances to help it out either, though its physical bulk is great. Movepool is basically limited to STAB + Earthquake, which isn't too bad but could be wider. Would probably go E just to be conservative, but I don't feel confident here either.
Sigilyph: I lean towards B-tier. It's obtained early and is immediately powerful, with great stats and strong STAB moves, and the first 2 gyms it faces are in its favour. It doesn't really have any favourable match-ups after that but it can still contribute against other gyms and remains useful as a fast and powerful route cleaner that doesn't really drop off. And having something to deal with the fighting trainers in Reflection Cave is handy in any case.
Slowbro/Slowking: I guess I could make a similar argument to Thick Club Cubone here and say that Compound Eyes give you a 20% chance of getting a King's Rock from Hariyama (or Hawlucha, but Hariyama is probably easier). That would give you a potentially instant evolution for Slowpoke, in which case I could see a case for at least D-tier for Slowking. However, if we decide that's too much of a bother than E-tier alongside Slowbro might be best. I couldn't stress enough just how bad Slowpoke is before it evolves, which pretty much kills spoils things for Slowbro.
Snubbull: D-tier is fine. I think C-tier would be a bit high because it's slow and kinda frail and has no STAB for a while. Maybe if it had retained its Normal typing it would be higher, but it didn't so no.
Solosis: Just want to point out that Duosion has identical Sp. Atk and Speed to Reuniclus, and it can hold Eviolite to help make up for its worse bulk. Therefore, late evolution isn't as bad for Solosis as it might seem at first, since its middle stage (obtained at Level 32) has comparable power to its final stage. It also gets Psyshock at level 25 for a powerful STAB. Could see a case for C-tier, but no higher than that since it doesn't have many favourable match-ups and it is SLOW.
Stunky: ugh why can't this learn Poison Jab by TM before it evolves? D-tier is probably fine but it has a few flaws, such as being weak initially and evolving a bit late into another Pokemon whose stats aren't that great. It has a few options for moves though: Thief from TM and Slash at level 22 is...ok. It can try a Toxic + Venoshock combo too. When it evolves, Poison Jab is immediately available to it for a good reliable STAB, and um...Flamethrower. It only has 1 weakness too, which means it can contribute against many gym leaders, etc. if not beat them outright.
Yanma: er yeah I was going to say something similar to Ondore about putting this in E-tier instead. Being horde only is bad enough, but just look at how terrible Yanma's movepool is early on. Aerial Ace off 65 Attack and Sonicboom are its best moves, and Uproar isn't really that good either. It evolves at level 33 and is finally able to learn Struggle Bug, but by then it 50 base power seems a bit underwhelming and you aren't getting much better than that until the move relearner. So maybe Yanmega has some use late-game which is enough to put it above F-tier, but I think that you have to put up with a lot prior to that, to the point where I'd say E-tier.