The following are known Action Replay Codes for No Rules: Get Phat 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
0d9136a5
316bc299
ed9f43f3
368b2a6b

Invincibility
0a8ac0e7
09583a0f

Infinite Lives
2e5c4e5a
c7577379

All Moves
1dbe35f0
c8c36cb6

Infinite Red Slingshots
928c7e94
ebbcd7b4

Infinite Green Slingshots
7737652c
915a4a42

Infinite Blue Slingshots
0c69a90b
295d4272

Max Score
be35cccd
587a45f2

Max Records
e77a7f21
488cb1a8

Press AR Button: Easy Boss Kills
91d1c4ec
0d6518c5
a05a144c
078b0074

Press AR Button: Easy Boss Kills
dba7c152
14d8a98d
a05a144c
078b0074

Press AR Button: Refill Health
8f0d9e58
88ce299f
0718ec2e
dbeb2e2c