Record Corner (FireRed/LeafGreen)
Unused map locations | Early English promotional Pokémon names | Eternal Flower Floette | Bird type | Unused music | Unused encounter system (Yellow) | Unused Bulbasaur slot machine symbol | Unused Shadow Pokémon | Cacophony | Unused Japanese list strings (Generation I) | Unused items | Unused Pokémon data | Unused and redundant Egg moves
See also:
S.S. Anne Ship Truck
In Pokémon FireRed and LeafGreen, the Record Corner from Pokémon Ruby and Sapphire and Pokémon Emerald (called "Record Center" in the English version release 1.0 of Ruby and Sapphire) exists as an unused map due to the removal of the record mixing feature. Stepping on the tiles used to trigger the feature causes the game to lock up as the relevant code has been deleted. The nurse's sprite was updated but interacting with her yields nothing.
External links
[1] - YouTube video of a player entering the Record Corner in Pokémon FireRed and LeafGreen.