These are the event Pokemon I have through legitimate means, to the best of my knowledge (someone I traded with may have gen'd them, or they may have been genned somewhere alone the line, but I only duplicated them).
If something isn't on this list, or you want a foreign one, I can probably help with that, I have a lot of Japanese ones, but listing those would be cancer.
-=Gen III=-
Wishmaker Jirachi
Mystery Mew
Space Center Deoxys
Jeremy
Ekans, Haunter (Gengar), Growlithe, Machoke (Machamp), Psyduck, Staryu, Tauros, Vulpix
Party of the Decade
Bulbasaur, Charizard, Blastoise, Pikachu, Alakazam, Articuno, Zapdos, Moltres, Dragonite, Typhlosion, Espeon, Umbreon, Raikou, Entei, Suicune, Tyranitar, Blaziken, Absol, Latias, Latios
-=Gen IV=-
Ash's Pikachu
GameStop Suicune
GameStop Entei
GameStop Raikou
Americas Winter 2011 Celebi
2010 World Championships Crobat
Video Game Championships 2010 Eevee
GameStop Jirachi
GameStop Pichu (Pikachu-coloured Pichu)
Toys "R" Us Arceus
2009 World Championships Weavile
US Video Game Championships 2009 Milotic
Toys "R" Us Regigigas
Toys "R" Us Shaymin
Nintendo Zone Pikachu
Toys "R" Us Dragonite
2008 World Championships Lucario
GameStop Deoxys
Nintendo World Store Darkrai
Nintendo World Store Manaphy
2007 TCG World Championships Pikachu
-=Gen V=-
International Summer 2013 Shiny creation trio/United States Summer 2013 Shiny creation trio
Giratina, Palkia, Dialga
2013 World Championships Smeargle
Ray Rizzo's Metagross
Toler Webb's Ludicolo
Spring 2013 Meloetta
Abram Burrows's Cloyster
Summer 2012 Keldeo
2012 World Championships Pikachu
Summer 2012 Pikachu
Video Game Championships 2012 Larvitar
Winter 2011 Darkrai
Zoroark Month Zoroark
2011 World Championships Scrafty
Summer 2011 Zoroark
Summer 2011 Karrablast
Summer 2011 Shelmet
Cilan's Pansage
Ash's Pidove
Iris's Axew
Plasma Deoxys
Winter 2013 Keldeo
Plasma Genesect
May 2012 Darkrai
Spring 2012 Pokémon
Reshiram, Zekrom
February 2012 Mewtwo
Movie 14 Victini
-=Gen VI=-
Pokémon the Series: XYZ Pokémon
Yveltal, Xerneas, Zygarde
Pokémon 20th Anniversary Mythical Pokémon
Meloetta, Keldeo, Victini, Shaymin, Manaphy, Jirachi, Celebi
Mac Hoopa
Sly Zoroark
Galileo Rayquaza
Hope Diancie
Steven's Beldum
Spooky 2014 Super Size Pumpkaboo
Summer 2014 Tough Pokémon
Heracross
Summer 2014 Poké Ball Pattern Vivillon
GTS Fancy Pattern Vivillon
XY Torchic
Helen Volcanion
Alexander Hoopa
N's Darmanitan
Cynthia's Garchomp
Play! Pokémon 2016 Mewtwo
Whitney's Miltank
Aldora Legendary birds
Articuno, Zapdos, Moltres
Lance's Dragonite
Pokémon 20th Anniversary Mythical Pokémon
Genesect, Arceus, Darkrai, Mew
PGL Delibird
PGL Pikachu
June 2015 Dragonite
PGL Amaura
PGL Tyrunt
Hidden Ability Present Pokémon
Serperior
Emboar
Samurott
October 2014 Pokémon
Diancie
Gengar
Winter 2013 Pokémon
Scizor
Garchomp
-=Gen 7=-
If it is english I probably have it.