The following are known Action Replay Codes for Madden NFL 06 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
e9c477b4
1e73264d
8d95bbc1
2e933bdb

Press L + Select: Home Team Wins
3cc647f8
224e66ef
d7aa304a
5af94136
70e1d76b
39618d19

Press R + Select: Away Team Wins
1523a49a
9d03f8fc
247f6fbb
8e90201e
13fa21e6
d32417b7

Press A + Select: 1st Down
d8b3d613
6ea775d4
f624f5e0
daf4dd1e

Press B + Select: 4th Down
e454226a
f3aa7b52
4cda6f4f
512cfaf0