The following are known Action Replay Codes for Army Men Advance 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
Master Code – Must Be On
3eaa2425
fde6fc67
9da121f0
b30229ac

The Enemy Has Bad Aim
014af80f
445829a3
8a5f969c
2555dd2e

Infinite Grenades
b1dc8e67
db796246

Infinite MG Ammo
a60ba9ad
2114f5d1

Have Rocket Launcher
bdee2e80
187bdad2

Have Flame Thrower
d82dd857
f80e2565

Camouflage Mode
bec79c7d
288be9b7

Push AR Button for Slow
dbba3a89
4cb74b94