Press R1 + R2 + L1 + L2 during game play, then activate the following effects by entering one of the codes. Note: Your Tree Of Wisdom must be a certain height before some codes can be enabled:

CHEAT FUNCTION - CHEAT CODE
Zombies wear sunglasses - future
Zombies have mustaches - mustache
Daisies appear when zombies die - daisies
Candy rains when zombies die - pinata
Toggles zombie call for brains sound - sukhbir
Zombies dance - dance
Zombies walks slowly - slowboke
Alternate Lawn Mower appearance - trickedout