Btw, I once was bored, and as I couldn't find a decent list on the webs (the one on serebii has like 4 codes, and some don't work), I've made a(n incomplete) list of GS codes for japanese Red/Green (here). Should them be added here as well?
Sure, go ahead. Good job with these!
I was under the impression that Serebii just added Pokémon Red/Blue Gameshark codes and labelled them as 'Pokémon Green codes', although it happens that not all Pokémon Red/Blue codes are identical to the Pokémon Red and Blue codes. You may have noticed that all the Japanese Gameshark codes for Generation I are the same; for example 01XXBFCF is the same code on Pocket Monsters Pikachu and Pocket Monsters Blue.
There was actually a similar thread
from 2008 like that, since these codes are really scarce without typing in Japanese characters themselves into search engines. Later GSCentral have started documenting Japanese Generation I Pokémon codes, I actually submitted a couple to their database; the database for Japan Generation I codes you can find here
Here are some Korean Pokémon Gold codes which I've just generated because there's actually at least one unique regional difference in this game believe it or not. Although it was released in 2002, making it one of the last Game Boy games ever. (I think the last official Game Boy Color game was a Doraemon Kanjii game released in 2003) I'll start a thread about this regional difference later.
The general idea for those is to add 0x01 to the first byte, then knock 0x43 from the second. (As a Gameshark code that's the other way round i.e. in 01XXYYZZ knock 0x43 from YY and add 0x01 to ZZ.)
01XXAAD1 (wild Pokémon modifier)
01XX00D1 (entrance modifier)
01XX01D1-01XX02D1 (area modifier)
01XX6BD6 (first item)
+1 of 6th digit for item/quantities 1-20
Also, IIMarckus documented all of the area digits
(note that these are for Crystal however). The Daycare Center one 0x0B, 0x18 took me to another route in Pokémon Gold, though I didn't test Crystal.