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I'll start.
>Pokémon Communication Center or PokéCom Center (PCC) (Pokémon Crystal, Japan)
https://www.youtube.com/watch?v=chmAMxlhh7o
>Mobile Connection (Pokémon Crystal, Japan)
https://www.youtube.com/watch?v=vM9l06N4YaA
>Mobile Center & Mobile Stadium (Pokémon Crystal, Japan)
https://www.youtube.com/watch?v=H2hXuKYJk_Y
>"Mobile Stadium" (Pokémon Stadium 2, Japan)
https://www.youtube.com/watch?v=DJHMcA-923s
>Pokémon Communication Center remix (Pokémon Ruby and Sapphire, unused)
https://www.youtube.com/watch?v=KWPmqykhGrM
>Johto Routes 38 & 39 remix (Pokémon Ruby and Sapphire, unused)
https://www.youtube.com/watch?v=qHBpU_K9Zuw
>Legendary beast battle remix (Pokémon Ruby and Sapphire, unused)
https://www.youtube.com/watch?v=kzUewliazHk
>Viridian/Pewter/Saffron/etc. remix (Pokémon Ruby and Sapphire, unused)
https://www.youtube.com/watch?v=wxHWHO9qDwQ
>Goldenrod Radio Tower Infiltrated by Team Rocket remix (Pokémon Ruby and Sapphire, unused)
https://www.youtube.com/watch?v=yZ16idg4QRg
>Pokémon Communication Center or PokéCom Center (PCC) (Pokémon Crystal, Japan)
https://www.youtube.com/watch?v=chmAMxlhh7o
>Mobile Connection (Pokémon Crystal, Japan)
https://www.youtube.com/watch?v=vM9l06N4YaA
>Mobile Center & Mobile Stadium (Pokémon Crystal, Japan)
https://www.youtube.com/watch?v=H2hXuKYJk_Y
>"Mobile Stadium" (Pokémon Stadium 2, Japan)
https://www.youtube.com/watch?v=DJHMcA-923s
>Pokémon Communication Center remix (Pokémon Ruby and Sapphire, unused)
https://www.youtube.com/watch?v=KWPmqykhGrM
>Johto Routes 38 & 39 remix (Pokémon Ruby and Sapphire, unused)
https://www.youtube.com/watch?v=qHBpU_K9Zuw
>Legendary beast battle remix (Pokémon Ruby and Sapphire, unused)
https://www.youtube.com/watch?v=kzUewliazHk
>Viridian/Pewter/Saffron/etc. remix (Pokémon Ruby and Sapphire, unused)
https://www.youtube.com/watch?v=wxHWHO9qDwQ
>Goldenrod Radio Tower Infiltrated by Team Rocket remix (Pokémon Ruby and Sapphire, unused)
https://www.youtube.com/watch?v=yZ16idg4QRg