Deoxys cause you can't get it.
well it is either mewtwo or entai/raikou/soucuin and no for leaf but yes to emerald
mew and mew two
By far, they have said Celebi is the hardest/rarest Pokemon to obtain outside of Japan.
the best Pokemon are mewto and the rarest Pokemon ever mew.
The rarest Pokemon is Munchlax, but you can find it only in the Valley Windworks honey tree.
well of course arceus but u can only get it on a wifi event
mew and mewtwo or possibly LAPRAZ it evolves from lapras at level 265 and is the hidden Pokemon 152!
It is believed that Chansey is the rarest Pokemon of all to catch in Pokemon FireRed and LeafGreen. It can only be found in the Safari Zone, near the north half of it.
my brother told me that it was on cinnabar island but i cant find it.
The rarest Pokemon is Dialga
there is no rarest Pokemon you have to train and train and including shinies there is no real rarest Pokemon at all.
deoxys and jirachi and there's even mewtwo in a secret place but that's for me to know and u to find out