Ursaring (thanks for noticing it was missing from this week, @xzini ): Skyridge 110/144 (although the Legendary Treasures RC16/RC25 artwork with Teddiursa is pretty nice as well)
Slugma: Skyridge 98/144
Magcargo: Great Encounters 45/106 (unlike Slugma the artworks of Magcargo are all a bit lackluster… - I don’t really like the snowy background of this artwork in particular given it’s a volcano-typed Pokémon, but the Magcargo itself and the pose is the best in this artwork, so I went with it regardless)
Swinub: Plasma Freeze 26/136
Piloswine: Stormfront 46/100
Corsola: EX Unseen Forces 37/115
Remoraid: Unleashed 59/59 (it kinda reminds me of a National Geographic documentary of salmon 
)
Octillery: Mysterious Treasures 57/123
Delibird: Japanese Pokémon VS 006/141
Mantine: HeartGold & SoulSilver 45/123
Skarmory: Great Encounters 53/106 and Boundaries Crossed 96/149 (I couldn’t choose again. I like the Great Encounters artwork of it sitting in its nest and also being closer, and I like the background of the Boundaries Crossed artwork and it really reminds me of blockbuster movies)
Houndour: Neo Discovery 39/75 (the background reminds me of the Pikachu & Pichu Bros anime short before the third movie 
)
Houndoom: Undaunted 5/90
Kingdra: XY39 Promo (with the Crystal Kingdra having a special place as well, since it’s the only reasonably rare card I pulled as a kid 
)
Phanpy: Aquapolis 100/147
Donphan: EX Ruby & Sapphire 17/109
Porygon2: Neo Destiny 8/105 (always loved its rainbow background - I also like the German Reverse Holo Triumphant 49/102 Porygon2 due to its very fitting misprint )
Stantler: Unleashed 64/95
Greetz,
Quuador