The following are known Action Replay Codes for Final Fight One on Nintendo Game Boy Advance (GBA).
These codes were also known as GameShark Codes and in most cases will work on both devices.

These codes are for the U.S. version of the game.

Master Code – Must Be On
2184b0fe
0828d52f
94f4637b
6bcc8cf4

Invincibility
629c5dab
ebb8a672

Infinite Time
a665b449
33a4db0b

Play As A-Guy
777a5369
922fe888

Play As Q-Cody
f6afc35a
bd289e73

Big Score
a5073527
a96035bd
c3a93984
036908fd
2a1c8f27
a5ad6595
1ca11708
d3449f2f
8b7f145c
8dfb9705

Press AR Button: Slow
dbba3a89
4cb74b94