There are the cheat codes from Ironzilla.com (as stated in the description), but I'm posting them for convenience. You can use them by pausing (shift) and clicking the red skull (top right).
Doom- This cheat code allows you to equip the MFG
Pantheon- This allows you to equip the God's Hand sword
I Am Legend- This cheat code allows you to start off with 3,000 zombies under the belt
Valkyrie- This is one of the best cheat codes for Zombocalypse, as it allows you to call in the chopper
Rambo- If you want the mini gun
Adrenaline- refill your health
Super Saiyan- If you want 3,000 experience points (only use once per game)
not sure if it's just me, but i think u can regen ur mp faster every time an ice golem hits you, so having high ice resist and having a mob of ice golems on u can be helpful
 "Tangerine Tycoon"){kind=icon}
 "Zombocalypse"){kind=icon}
 "Hack Slash Crawl"){kind=icon}
 "Epic Battle Fantasy 2"){kind=icon}
 "Soccer Physics"){kind=icon}
 "Bloons TD 5"){kind=icon}
 "Flappy Bird Flash"){kind=icon}
 "Scribble 2!"){kind=icon}
 "StrikeForce Kitty"){kind=icon}
 "Pirate Defense"){kind=icon}
 "The Valley Rule"){kind=icon}
 "Hippolyta"){kind=icon}
 "Escape From 26"){kind=icon}
 "Realm of the Mad God"){kind=icon}