theSLAYER

This gift was distributed as part of the Pokémon Adventure 25 (Grab these Mythicals) campaign.
The gift codes can be obtained via exchanging scraps for codes.

User could exchange their scraps on this site: http://adventure25pokemonkorea.co.kr/
Do note this site limits access to Korean IP only.

   Wonder Card ID #1014: Mythical Pokémon Marshadow Gift  Species   Marshadow   TID   210426   Distribution   Serial Code   Location   a lovely place   Dates   Apr 26 to Oct 31, 2021   PID   Cannot Be Shiny   Games   SWSH   Nature   Random   Ability   Technician (1)   Item   None    IVs   EVs HP RND,
3x
31 IVs   ALL
0 ATK DEF S.ATK S.DEF SPE
  Lv. 60       Moves   (ITALIC means Relearnable)   Spectral Thief   Drain Punch   Force Palm   Shadow Sneak

Classic Ribbon  Lang
 Slot  Mon's
 Lang  Nickname  OT Name OT's 
Lang   JPN  마샤도  어드벤처  KOR  ENG  마샤도  어드벤처  KOR  FRE  마샤도  어드벤처  KOR  ITA  마샤도  어드벤처  KOR  GER  마샤도  어드벤처  KOR  SPA  마샤도  어드벤처  KOR  KOR  마샤도  어드벤처  KOR  CHS  마샤도  어드벤처  KOR  CHT  마샤도  어드벤처  KOR Only One Redemption Allowed  Format Ver.2.1.0-2b, Post Updated Date:20210426_1631

This is a Wild Area event held by Sword and Shield. This event does not appear to host any Gigantamaxes.
This raid gives players a chance to land on a slot with a guaranteed shiny Eiscue, 2% chance at 5 star raids.
Every slot gives players an encounter with Eiscue, to commemorate the World Penguin Day.
 
To import these files into your save, use PKHeX's block importing function. Our tutorial should guide you through it.
Our first post of this page contains some data relevant to the importing stage.
There's info and some common questions regarding Wild Area Events here.
To see other Wild Area Events, here.

A phony Sinistea with 6 0IVs. Use the shiny file it you want a shiny version, and the non-shiny file if you want a non-shiny.

You could replace the species, moves, location, level, ball and get what you want as a Six 0IVs mon.
If you want perfect IVs in any stat, you should perform hyper training on that stat.
If you want, you may also change Stat Nature.

Things you should not change:
PID, Nature, Height, Weight, IVs, EC.
If you want to change TID, SID, the shiny entry must remain Square Shiny with the appropriate PID.
(Or alternatively it can be Star Shiny, with the corresponding TID/SID on the then non-shiny file)
 
You can also get a 0IV mon easily using the Auto Legality Mod.
 

Distribution Title メガトウキョーの　リザードン Wondercard ID 139     PID Shiny PID     Games ORAS Type Local Wi-Fi Dates Jan 1 to
31, 2016 Species Charizard Nickname (default) Gender Male/Female Level 36 Nature Random Ability Blaze (1) OT メガトウキョ TID 12124 Location a Pokémon Center Ribbon Premier Ball Cherish Ball Held Item Charizardite Y Moves Overheat Solar Beam Focus Blast Hold Hands Relearn
Moves Hold Hands (None) (None) (None) Receiving Text 0x07 Thank you for coming to the Pokémon Center! Please pick up your gift from the delivery girl in the game.

This is a Wild Area event held by Sword and Shield. This event hosts Gigantamax Hatterene and Gigantamax Corviknight.
To import these files into your save, use PKHeX's block importing function. Our tutorial should guide you through it.
Our first post of this page contains some data relevant to the importing stage.
There's info and some common questions regarding Wild Area Events here.
To see other Wild Area Events, here.

Extra info:
Index 059 has Hattrem encounters with the Gigantamax factor. It appears that it may be unattended, as Corvisquire does not get the same treatment.

This is a Wild Area event held by Sword and Shield. This Max Raid event was distributed to players to commemorate the Pokémon Day 2021.
This Max Raid event adds Gigantamax Pikachu as a possible encounter into the previous Max Raid encounters.
This event also has an increased chance of landing a Shiny Gigantamax Pikachu; players have a 2% chance of landing on a guaranteed Shiny, only at the 5 star tier.
Besides that, there are also specific rewards for the amount of times Max Raid Battles against Gigantamax Pikachu were won:
1,000,000 battles won: players receive 100 Armorite Ore and 100 Dynite Ore.
To import these files into your save, use PKHeX's block importing function. Our tutorial should guide you through it.
Our first post of this page contains some data relevant to the importing stage.
There's info and some common questions regarding Wild Area Events here.
To see other Wild Area Events, here.

It appears that this Toxtricity was distributed to players to commemorate the then new TCG release: Shining Fates
It was first known to be distributed via Pokémon Pass to players who visited Gamestop (inside, or curbside), and was later known to be available via various sites across Europe.
The form and nature is locked.


 Wonder Card ID #0509: Shiny Toxtricity Gift  Species   Toxtricity   TID   210219   Distribution   Serial Code   Location   a lovely place   Dates   Feb 19 to Jun 30, 2021   PID   Shiny PID: D8302802   Games   SWSH   Nature   Rash   Ability   Punk Rock (1)   Item   Throat Spray    IVs   EVs HP ALL
RND   ALL
0 ATK DEF S.ATK S.DEF SPE
  Lv. 50       Moves   (ITALIC means Relearnable)   Overdrive   Sludge Wave   Boomburst   Rising Voltage

Classic Ribbon  Lang
 Slot  Mon's
 Lang  Nickname  OT Name OT's 
Lang   JPN  (default name)  Rock Star  JPN  ENG  (default name)  Rock Star  ENG  FRE  (default name)  Rock Star  FRE  ITA  (default name)  Rock Star  ITA  GER  (default name)  Rock Star  GER  SPA  (default name)  Rock Star  SPA  KOR  (default name)  Rock Star  KOR  CHS  (default name)  Rock Star  CHS  CHT  (default name)  Rock Star  CHT Only One Redemption Allowed  Format Ver.2.1.0-2b, Post Updated Date:20210219_1948

Ahiru's Wonderland is apparently an infamous site that hoards event Pokemon from Japan, back in Gen 3 days.

Relevant screenshots of the page will match the relevant save data uploaded.
 
Jan 1, 2019 edit: @shadowofdarkness shared some files he downloaded, probably back in 2007.
Interestingly, it went beyond Gen 3, and contained various Gen 4 files.

Do note that:
1. .stk files are a bulk batch of files used with pokestock
2. There appears to be some files being marked (with Pokerus) in the saves, use at your own risk.

When players interact with a particular gravestone along the grasslands of Ballimere Lake, the words "let my voice be heard" is etched into it. When the player then goes to talk to 32 players in the vicinity, and the gravestone would then have the text "my voice has been heard".
After that, when the player reloads the area, a Spiritomb will be in the over world awaiting battle.
This encounter can be shiny.

After the player captures Cobalion, Terrakion, and Virizion in Crown Tundra, and report back to Sonia, and she then proceeds to leave, a new pair of footprints will appear near the cooking pot found at the small island near the Dyna Tree Hill. If the player fulfills 2 requirements, being (a) have the aforementioned 3 in party (can be caught in Crown Tundra or HOME transferred) during (b) cooking curry in camp, a wild Keldeo will appear on that island.
This Keldeo encounter is shiny locked.

After the player triggers the roaming event for Galarian Articuno, Galarian Zapdos and Galarian Moltres at the Dyna Trill Hill, the birds will begin roaming.

Galarian Articuno roams along Crown Tundra, Galarian Zapdos roams along the mainland Galar's Wild Area, and Galarian Moltres roams along the Isle of Armor.

After the player triggers the roaming event for Galarian Articuno, Galarian Zapdos and Galarian Moltres at the Dyna Trill Hill, the birds will begin roaming.

Galarian Articuno roams along Crown Tundra, Galarian Zapdos roams along the mainland Galar's Wild Area, and Galarian Moltres roams along the Isle of Armor.

After the player triggers the roaming event for Galarian Articuno, Galarian Zapdos and Galarian Moltres at the Dyna Trill Hill, the birds will begin roaming.

Galarian Articuno roams along Crown Tundra, Galarian Zapdos roams along the mainland Galar's Wild Area, and Galarian Moltres roams along the Isle of Armor.

A simple program for those who struggle with the tutorial guide for shiny Cute Charm abuse.
Really easy to use.
Input Specifics (if you care), then hit Generate, then input the TID/SID for your trainer into your save, and ensure your cute charm lead has the right gender.

Note: This program will not generate a bunch of different TID/SID pairs.
It was programmed to only have one pair per option. If you want different pairs from what's listed, follow the guide.
 
Prerequisite: Ability to read, able to edit saves with PKHeX, able to backup and restore (edited and unedited) saves from your device/emulator.

Distribution Title Charizard and a Charizardite X! Wondercard ID 516     PID Cannot Be Shiny Games Y Type Nintendo Zone/Serial Code Dates Jul 11 -
Aug 10, 2014 Species Charizard Nickname (default) Gender Male Level 36 Nature Random Ability Blaze (1) OT GAME 2014 TID 7114 Location a lovely place Ribbon http://events.projectpokemon.org/images/Classic_Ribbon.png Classic , Ball http://events.projectpokemon.org/images/ball-cherish.png Cherish Ball Held Item http://events.projectpokemon.org/images/items/charizardite-x.png Charizardite X Moves http://events.projectpokemon.org/images/dragon.pngDragon Rage http://events.projectpokemon.org/images/fire.pngFire Fang http://events.projectpokemon.org/images/flying.pngAir Slash http://events.projectpokemon.org/images/dragon.pngDragon Claw Relearn
Moves http://events.projectpokemon.org/images/type-none.png(None) http://events.projectpokemon.org/images/type-none.png(None) http://events.projectpokemon.org/images/type-none.png(None) http://events.projectpokemon.org/images/type-none.png(None) Receiving Text 0x35 Thank you for receiving this distribution! Please pick up your gift from the delivery girl in any Pokémon Center.

Distribution Title Charizard and a Charizardite Y! Wondercard ID 516     PID Cannot Be Shiny Games X Type Nintendo Zone/Serial Code Dates Jul 11 -
Aug 10, 2014 Species Charizard Nickname (default) Gender Male Level 36 Nature Random Ability Blaze (1) OT GAME 2014 TID 7114 Location a lovely place Ribbon http://events.projectpokemon.org/images/Classic_Ribbon.png Classic , Ball http://events.projectpokemon.org/images/ball-cherish.png Cherish Ball Held Item http://events.projectpokemon.org/images/items/charizardite-y.png Charizardite Y Moves http://events.projectpokemon.org/images/fire.pngFire Fang http://events.projectpokemon.org/images/fire.pngFlame Burst http://events.projectpokemon.org/images/flying.pngAir Slash http://events.projectpokemon.org/images/fire.pngInferno Relearn
Moves http://events.projectpokemon.org/images/type-none.png(None) http://events.projectpokemon.org/images/type-none.png(None) http://events.projectpokemon.org/images/type-none.png(None) http://events.projectpokemon.org/images/type-none.png(None) Receiving Text 0x35 Thank you for receiving this distribution! Please pick up your gift from the delivery girl in any Pokémon Center.  

@ajxpk's gif for the Eon Ticket process, with the English Version as an example:


Original Thread and Credits!

This page holds the Pokemon FireRed & LeafGreen Version and Pokemon Emerald Version of the Mystic Ticket.
The wonder card is not interchangeable between the versions.

Original Thread and Credits!

This Mystery Event Wonder Card is only legal for the Japanese Copy of Pokemon Emerald!

For PokéPark Japan, the Old Sea Map was distributed via both NDS download play and GBA wireless system (translated article in image)

Original Thread and Credits!

This Mew was distributed at PokéPark in Taiwan in 2006.
The OT can be Male or Female.
 
 Species   Mew   Nickname   ミュウ    OT   ポケパーク   TID   60510   Distribution   trade / machine   Location   (Fateful Encounter)   Dates   May 10 to Jun 04, 2006   PID   Cannot Be Shiny   Games   RSE FRLG    Lv. 30                                                                  Nature   Random   Ability   Synchronize (1)   Item   None      Moves       Pound   Transform   Mega Punch   Metronome

This gift was distributed during the screening of M08: Lucario and the Mystery of Mew in Japan.
This gift in particular was distribution via the Download Play feature of the NDS, meaning it could only be redeemed on the NDS, and not a GBA.

The distribution period was between September 1 to September 25, 2005.

This gift was distributed during the screening of M08: Lucario and the Mystery of Mew in Japan.
This gift in particular was distribution via the Download Play feature of the NDS, meaning it could only be redeemed on the NDS, and not a GBA.

The distribution period was between September 1 to September 25, 2005.

This Celebi was distributed at PokéPark in Taiwan in 2006.
This page host a select few individual files, and an archive of all of them.
The OT can be Male or Female.
 
 Species   Celebi   Nickname   セレビィ    OT   ポケパーク   TID   60623   Distribution   trade / machine   Location   (fateful encounter)   Dates   Jun 23 to Sep 24, 2006   PID   Cannot Be Shiny   Games   RSE FRLG    Lv. 30                                                                  Nature   Random   Ability   Serene Grace (1)   Item   None      Moves       Heal Bell   Safeguard   Ancient Power   Future Sight

#pk3archive

Through the narrative of the story, the player battles Spectrier once, but is unable to capture it.
Instead, the player catches a Rider Calyrex (a Calyrex fused with Glastrier or Spectrier).
Spectrier can be obtained by unfusing the Shadow Rider Calyrex that was caught.

Whether Calyrex is fused with Glastrier or Spectrier, depends on the choice the player made during the story.

Through the narrative of the story, the player battles Glastrier once, but is unable to capture it.
Instead, the player catches a Rider Calyrex (a Calyrex fused with Glastrier or Spectrier).
Glastrier can be obtained by unfusing the Ice Rider Calyrex that was caught.

Whether Calyrex is fused with Glastrier or Spectrier, depends on the choice the player made during the story.