D64D (Lorelei's Pokémon League room)= 07 : You start an endless loop of Hall of Fame inductions after entering Lorelei's room, an ACE setup apparently isn't even needed
D64C (Blue's Pokémon League room)= 0E : Arbitrary code execution at D321 in WRAM. Yes, that's right! It executes item 2's quantity without the need of a bootstrap setup
In addition there is one that could be useful for Lorelei's room, if there is an equivalent script in Japanese Red/Green/Blue.
0x10: Although it first appears to have no use other than hiding the player sprite, an invisible menu with options is opened (possibly badge describer man). If the player waits until a description has finished and holds down at the entrance, they may successfully leave Lorelei's room. It is unknown whether a similar effect occurs in the Japanese versions, which could be useful for badge describer glitch.
This is amazingly lucky.