This thread aims to foster discussion on what are the best options to experience the grace and opulence of Sinnoh. For that purpose, the available Pokémon will be ranked in six tiers.
Do keep in mind that these descriptions aren't exactly rules, but merely a guideline.
What is a rule, however, is that a Pokémon's tier is not relative to one another. Each mon will earn their ranks on their own.
S-Tier
These Pokémon don't just stand at the top, they go beyond the scale and are extremely efficient. There is no point they'll be dead weight, and if there is, they'll just destroy the game afterward like RBY Alakazam. Do NOT treat this as merely "Top Tier", these Pokémon go even further beyond.
A-Tier
These Pokémon are highly efficient and well-recommended but have minor flaws that prevent them from being broken such as a crippling matchup, availability issues or a weak period without absolute dominance afterward.
B-Tier
These Pokémon are efficient, but not as reliable as the A-Tiers due to having noticeable flaws such as poor coverage, a long period of mediocrity or severe availability issues.
C-Tier
These Pokémon are solid but will require significant support to reach their full potential.
D-Tier
These Pokémon are decent. They'll have significant flaws but will get you to the endgame provided with the proper support.
E-Tier
These Pokémon are bad. You will have to drag them kicking and screaming to the endgame, but they will get there eventually. I think.
F-Tier
These Pokémon are as efficient and fun to use as doing a Wynaut solo run. Not even Wobbuffet. Everstone Wynaut. No Leftovers for passive healing.
There are several criteria that define a Pokémon's In-Game Viability. Similarly, this isn't a checklist, just a guideline.
Availability: This is how early a Pokémon becomes available in the game, with relevant factors such as encounter rate, level, backtracking, and significant HM usage also being considered.
Typing: A Pokémon's typing can make the difference between whether or not it has a positive matchup or even a section of the game where it struggles, such as RSE's infamous "Too much water" section where you will face problems if your Pokémon can't effectively deal with Water-types.
Stats: Rather self-explanatory. Good stats are good, and naturally they have a big influence on a Pokémon's viability.
Movepool: A Pokémon's movepool is of great importance to whether or not it is truly able to be used to its full potential. TMs and HMs are allowed, but there are penalties for overreliance on highly contested TMs since the mon gets a cost associated to them to reach satisfying results.
Major Battles: Major battles consist of Gym Leaders, the Elite 4, Rival, and higher-ranked Villain operatives such as the Admins.
Granted, Sinnoh graces veterans with several difficult trainers outside of those, but they're not as impactful or memorable as anyone with a unique sprite.
Other: Factors like Evolution methods, abilities, and the like.
To avoid any potential issues, some rules and guidelines will be established so that newcomers can understand how this kind of tier works.
This list is NOT Speedrun-oriented.
Think about an efficient run as a casual run. You're picking up a game to have fun and clear it within a reasonable timeframe. The main question this thread answers is: "Which mons are going to get me to the post-game with the least hassle?"
The standard for In-Game Tier Lists assume the player runs four Pokémon.
However, this is a guideline, anywhere between 4~6 is fine. Do keep in mind that 3 or less Pokémon are prone to be overleveled and therefore render their test results ineligible.
Deliberately overleveling is strictly prohibited.
It's understandable if you wind up fighting too many trainers and get one or two levels ahead of a non-Gym Leader major battle. It is not to deliberately do so. In the case it happens, even if it's just one level, let the thread know so it'll be taken into account.
Be transparent and honest with your routing.
The Sinnoh games are the only ones in the series where there is a clear incentive to beat all trainers. Beating all of them guarantees you'll have seen all Pokémons and therefore unlock the National Dex at the end of the game.
This list does not account for that, however, it is understandable if you wish to do so and still contribute. Just make sure to let the thread know that you're beating all trainers and don't overlevel.
As a general rule of thumb, the more information you provide about your run, the better people can evaluate your testing results.
Similarly, if appliable, it is important to tell whether or not a Pokémon got vitamins, Rare Candies and the like, which leads to this rule...
Dumping non-renewable resources on one Pokémon is considered highly inefficient for the purposes of this list.
There are obvious reasons for that. The first is that if you're dumping resources on one mon, the other three will be just sitting on their thumbs. The other is that these inherently create a distortion of the Pokémon's real performance, which makes your test results inconclusive.
TMs are allowed, but if a Pokémon relies on too many one-use TMs to be efficient, that's obviously a problem.
X-Items are banned.
Similarly to the above, they distort test results by mixing an external factor to give a Pokémon a boost it wouldn't normally get.
I don't care how cheap or efficient they are, they're essentially the equivalent to steroids.
Trade Evolutions are allowed, provided the tester provides the necessary items when appliable.
Basically, this means that in the case of Pokémon like Scyther, the tester will need to find the Metal Coat and then trigger the trade evolution by trading back and forth. Outside influences like Pokémon being traded from other games are strictly banned.
Think about an efficient run as a casual run. You're picking up a game to have fun and clear it within a reasonable timeframe. The main question this thread answers is: "Which mons are going to get me to the post-game with the least hassle?"
The standard for In-Game Tier Lists assume the player runs four Pokémon.
However, this is a guideline, anywhere between 4~6 is fine. Do keep in mind that 3 or less Pokémon are prone to be overleveled and therefore render their test results ineligible.
Deliberately overleveling is strictly prohibited.
It's understandable if you wind up fighting too many trainers and get one or two levels ahead of a non-Gym Leader major battle. It is not to deliberately do so. In the case it happens, even if it's just one level, let the thread know so it'll be taken into account.
Be transparent and honest with your routing.
The Sinnoh games are the only ones in the series where there is a clear incentive to beat all trainers. Beating all of them guarantees you'll have seen all Pokémons and therefore unlock the National Dex at the end of the game.
This list does not account for that, however, it is understandable if you wish to do so and still contribute. Just make sure to let the thread know that you're beating all trainers and don't overlevel.
As a general rule of thumb, the more information you provide about your run, the better people can evaluate your testing results.
Similarly, if appliable, it is important to tell whether or not a Pokémon got vitamins, Rare Candies and the like, which leads to this rule...
Dumping non-renewable resources on one Pokémon is considered highly inefficient for the purposes of this list.
There are obvious reasons for that. The first is that if you're dumping resources on one mon, the other three will be just sitting on their thumbs. The other is that these inherently create a distortion of the Pokémon's real performance, which makes your test results inconclusive.
TMs are allowed, but if a Pokémon relies on too many one-use TMs to be efficient, that's obviously a problem.
X-Items are banned.
Similarly to the above, they distort test results by mixing an external factor to give a Pokémon a boost it wouldn't normally get.
I don't care how cheap or efficient they are, they're essentially the equivalent to steroids.
Trade Evolutions are allowed, provided the tester provides the necessary items when appliable.
Basically, this means that in the case of Pokémon like Scyther, the tester will need to find the Metal Coat and then trigger the trade evolution by trading back and forth. Outside influences like Pokémon being traded from other games are strictly banned.
To assist players, there is an Availability List showing where and when you can catch one of Sinnoh's excellent Pokémon.
This list was shamelessly stolen from the previous thread, so shoutouts and likes to sin(pi) for their good work.
The following information contains spoilers. If you don't want to be spoiled, look away now!
So far this is only complete for Platinum
LEGEND
[G] = This Pokémon is given to you by a NPC (possibly as an Egg).
[IN] = This Pokémon is an interactable encounter.
[T] = This Pokémon is obtained via in-game trade.
[D] = This Pokémon can only be caught in Pokémon Diamond.
[D*] = This Pokémon is first found here in Pokémon Diamond only.
[P] = This Pokémon can only be caught in Pokémon Pearl.
[P*] = This Pokémon is first found here in Pokémon Pearl only.
[Pt] = This Pokémon can only be caught in Pokémon Platinum.
[Pt*] = This Pokémon is first found here in Pokémon Platinum only.
Untiered Pokémon
Cresselia - Not available until Postgame
Heatran - Not available until Postgame
Giratina (D/P), Dialga/Palkia (Pt) - Not available until Postgame
Any other Pokémon not obtainable before beating the Champion, or that can only be obtained via earlier Generations or Events.
So far this is only complete for Platinum
LEGEND
[G] = This Pokémon is given to you by a NPC (possibly as an Egg).
[IN] = This Pokémon is an interactable encounter.
[T] = This Pokémon is obtained via in-game trade.
[D] = This Pokémon can only be caught in Pokémon Diamond.
[D*] = This Pokémon is first found here in Pokémon Diamond only.
[P] = This Pokémon can only be caught in Pokémon Pearl.
[P*] = This Pokémon is first found here in Pokémon Pearl only.
[Pt] = This Pokémon can only be caught in Pokémon Platinum.
[Pt*] = This Pokémon is first found here in Pokémon Platinum only.
===START===
Route 201: Turtwig [G], Chimchar [G], Piplup [G]
Route 201 (after capture tutorial): Starly, Bidoof, Kricketot
Route 202: Shinx
Old rod: Magikarp
Route 204 south: Budew, Wurmple, Zubat
Ravaged Path: Psyduck
Route 203: Abra
Oreburgh Gate: Geodude
Oreburgh City: Abra [T]
Route 207: Machop, Ponyta
Oreburgh Mine: Onix
===GYM 1===
VALLEY WINDWORKS: Buizel, Pachirisu, Shellos
Honey trees: Aipom, Heracross, Burmy, Combee, Cherubi
Note that the first Munchlax tree can range from this point to after Surf becomes usable.
VALLEY WINDWORKS (after defeating Mars): Drifloon [IN]
ETERNA FOREST: Gastly, Hoothoot, Buneary
ETERNA CITY - Chatot [T]
UNDERGROUND - Shieldon [P/Pt] [Fossil], Cranidos [D/Pt] [Fossil]
Route 211 west: Meditite, Chingling, Bronzor
Mt. Coronet 1F: Cleffa, Nosepass [Pt]
===GYM 2===
Old Chateau: Rotom [Pt]
Eterna City (after defeating Jupiter): Togepi [Pt][G]
Route 206: Gligar [Pt]
WAYWARD CAVE: Gible [Pt*]
Route 208: Ralts [Pt]
Hearthome CITY: Eevee [Pt][G]
===GYM 3===
Route 209: Chansey, Duskull [Pt], Spiritomb [IN] (if yes trade)
Good rod: Goldeen, Barboach, Finneon
Solaceon Ruins: Unown
Route 210 south: Scyther [Pt]
Route 215: Lickitung [Pt], Marill
Veilstone City: Porygon [Pt][G]
Route 214: Rhyhorn [Pt], Houndour [Pt]
Ruin Maniac Cave: Hippopotas
Valor Lakefront: Girafarig
Route 213: Remoraid, Wingull
Route 212 south: Quagsire, Croagunk
Trophy Garden: Pichu
Great Marsh: Tangela [Pt], Yanma [Pt], Tropius [Pt], Skorupi, Carnivine
===GYM 4===
===GYM 5===
Route 210 north: Swablu [Pt]
Surf: Tentacool
Route 221: Sudowoodo [Pt*]
Fuego Ironworks: Magnemite [Pt], Magmar [Pt]
Route 218: Mr. Mime [Pt*]
Iron Island: Steelix (Wild), Riolu [G]
===GYM 6===
Mt. Coronet B1F: Feebas
Route 216: Sneasel, Snorunt [Pt], Snover
Route 217: Swinub [Pt]
SNOWPOINT CITY: - Haunter [T]
===GYM 7===
Mt. Coronet mountainside: Absol [Pt]
Distortion World: Giratina [Pt][IN]
Lake Acuity: Uxie [IN]
Lake Valor: Azelf [IN]
Lake Verity: Mesprit [roaming]
Route 222: Electabuzz [Pt]
Route 223: Mantyke
Route 201: Turtwig [G], Chimchar [G], Piplup [G]
Route 201 (after capture tutorial): Starly, Bidoof, Kricketot
Route 202: Shinx
Old rod: Magikarp
Route 204 south: Budew, Wurmple, Zubat
Ravaged Path: Psyduck
Route 203: Abra
Oreburgh Gate: Geodude
Oreburgh City: Abra [T]
Route 207: Machop, Ponyta
Oreburgh Mine: Onix
===GYM 1===
VALLEY WINDWORKS: Buizel, Pachirisu, Shellos
Honey trees: Aipom, Heracross, Burmy, Combee, Cherubi
Note that the first Munchlax tree can range from this point to after Surf becomes usable.
VALLEY WINDWORKS (after defeating Mars): Drifloon [IN]
ETERNA FOREST: Gastly, Hoothoot, Buneary
ETERNA CITY - Chatot [T]
UNDERGROUND - Shieldon [P/Pt] [Fossil], Cranidos [D/Pt] [Fossil]
Route 211 west: Meditite, Chingling, Bronzor
Mt. Coronet 1F: Cleffa, Nosepass [Pt]
===GYM 2===
Old Chateau: Rotom [Pt]
Eterna City (after defeating Jupiter): Togepi [Pt][G]
Route 206: Gligar [Pt]
WAYWARD CAVE: Gible [Pt*]
Route 208: Ralts [Pt]
Hearthome CITY: Eevee [Pt][G]
===GYM 3===
Route 209: Chansey, Duskull [Pt], Spiritomb [IN] (if yes trade)
Good rod: Goldeen, Barboach, Finneon
Solaceon Ruins: Unown
Route 210 south: Scyther [Pt]
Route 215: Lickitung [Pt], Marill
Veilstone City: Porygon [Pt][G]
Route 214: Rhyhorn [Pt], Houndour [Pt]
Ruin Maniac Cave: Hippopotas
Valor Lakefront: Girafarig
Route 213: Remoraid, Wingull
Route 212 south: Quagsire, Croagunk
Trophy Garden: Pichu
Great Marsh: Tangela [Pt], Yanma [Pt], Tropius [Pt], Skorupi, Carnivine
===GYM 4===
===GYM 5===
Route 210 north: Swablu [Pt]
Surf: Tentacool
Route 221: Sudowoodo [Pt*]
Fuego Ironworks: Magnemite [Pt], Magmar [Pt]
Route 218: Mr. Mime [Pt*]
Iron Island: Steelix (Wild), Riolu [G]
===GYM 6===
Mt. Coronet B1F: Feebas
Route 216: Sneasel, Snorunt [Pt], Snover
Route 217: Swinub [Pt]
SNOWPOINT CITY: - Haunter [T]
===GYM 7===
Mt. Coronet mountainside: Absol [Pt]
Distortion World: Giratina [Pt][IN]
Lake Acuity: Uxie [IN]
Lake Valor: Azelf [IN]
Lake Verity: Mesprit [roaming]
Route 222: Electabuzz [Pt]
Route 223: Mantyke
Untiered Pokémon
Cresselia - Not available until Postgame
Heatran - Not available until Postgame
Giratina (D/P), Dialga/Palkia (Pt) - Not available until Postgame
Any other Pokémon not obtainable before beating the Champion, or that can only be obtained via earlier Generations or Events.
To further assist testers and players, I prepared an availability list for all the relevant evolutionary items for DPPt In-Game Tiering.
===GYM 2===
Up-Grade: Team Galactic Eterna Building. (Plat)
===GYM 3===
Magmarizer: Route 214. (Plat)
Oval Stone: Lost Tower.
Razor Fang: Route 214. (Plat)
===GYM 5===
Electirizer: Valley Windworks. (Requires Surf - Plat)
Metal Coat: Iron Island. (Guaranteed)
Held by wild Magnemite, wild Steelix, wild Bronzor, and wild Bronzong (5% chance each)
The Thief TM can be obtained in Eterna City and Bronzor is available before Gym 2. It is however, quite time-consuming to attempt to steal a Metal Coat.
Protector: Iron Island. (Plat)
===GYM 7===
Dubious Disc: Veilstone - Team Galactic HQ. (Plat)
Razor Claw: Veilstone - Team Galactic HQ. (Plat)
Reaper Cloth: Acuity Lakefront (Requires Rock Climb - Plat)
===GYM 8===
Razor Claw: Victory Road (All),
Up-Grade: Team Galactic Eterna Building. (Plat)
===GYM 3===
Magmarizer: Route 214. (Plat)
Oval Stone: Lost Tower.
Razor Fang: Route 214. (Plat)
===GYM 5===
Electirizer: Valley Windworks. (Requires Surf - Plat)
Metal Coat: Iron Island. (Guaranteed)
Held by wild Magnemite, wild Steelix, wild Bronzor, and wild Bronzong (5% chance each)
The Thief TM can be obtained in Eterna City and Bronzor is available before Gym 2. It is however, quite time-consuming to attempt to steal a Metal Coat.
Protector: Iron Island. (Plat)
===GYM 7===
Dubious Disc: Veilstone - Team Galactic HQ. (Plat)
Razor Claw: Veilstone - Team Galactic HQ. (Plat)
Reaper Cloth: Acuity Lakefront (Requires Rock Climb - Plat)
===GYM 8===
Razor Claw: Victory Road (All),
There is a very important item outside of the scope of this list but it absolutely warrants a mention...
The Choice Specs are available in Celestic Town.
You can obtain them from an NPC in the Mart during the morning. During other times of the day, the NPC will give out other glasses-like items like the Blackglasses.
Diamond and Pearl have significant differences to Pokémon Platinum, such as the lack of the Dex Expansion, several differences regarding the level curve, most notably at the E4, and Fantina as the 5th Gym Leader, where her Mismagius isn't as much of a threat.
However, for their poor reputation as unoptimized games, there may not be enough testers up to the challenge of exploring Sinnoh's humble beginnings. Therefore, I'm making a poll.
Do you want Diamond and Pearl to have a separate thread and are willing to test Pokémon so it can be completed?
> Yes
> No
To answer it, simply copy and paste one of the following so it's easier to find with the search function:
"DP Thread Split > Yes"
"DP Thread Split > No"
If you just wish to talk about testing and nominations for these games in this thread, simply denote these as you would in other In-Game Thread Lists.
However, for their poor reputation as unoptimized games, there may not be enough testers up to the challenge of exploring Sinnoh's humble beginnings. Therefore, I'm making a poll.
Do you want Diamond and Pearl to have a separate thread and are willing to test Pokémon so it can be completed?
> Yes
> No
To answer it, simply copy and paste one of the following so it's easier to find with the search function:
"DP Thread Split > Yes"
"DP Thread Split > No"
If you just wish to talk about testing and nominations for these games in this thread, simply denote these as you would in other In-Game Thread Lists.
With all of that out of the way, it's time to experience greatness. 
