Easy Pokemon
A new pokemon can be obtained once a day via spot pass. If you change the date on the 3ds when you go back into the game you get the message that a new pokemon has arrived. Do this indefinitely to catch 'em all.
The following are known Action Replay Codes for Pokemon Fire Red Version on Nintendo Game Boy Advance (GBA).
These are Action Replay Version 3 (V3) Codes.
The codes should work with the region specified but may work for other regions as well.
(M)
e6a003d6
8110ddd5
a47fb2dc
1af3ca86
24c35e88...