Here you go.

Invincible

To make yourself invincible do this:

Pause game. Press and Hold L2.
Then press: Square : Circle : Left : Left : Circle :Square

Weapons upgrade

If you use the Invincible code on board the mothership the cheat makes all upgrades for your unlocked weapons available at Pox's Laboratory


Unlimited Ammunition
Pause the game. Press and hold L2.
Then Enter: Left : Circle : R2 : Right : R1 : Square.


Endless Mind Power

With this the MC meter will never decrease. Make sure it is above zero before activating.

Pause the game. Press and Hold L2.
Then Enter: R1 : R2 : Circle : Right : R2 : Circle.


Alert Meter At Max

Enter start menu, press and hold L2
Then enter: Right : Square : R2 : R1 : Right : R2.


Boost DNA

This cheat code have to be entered on the Mothership.

Enter start menu. Press and hold L2.
Then enter: R1 : R1 : R2 : R2 : Left : Right : Left : Right : R2.


Alert Meter Reset

Enter the start menu. Press and hold L2.
Then enter: Right : R2 : R1 : Square : Right.

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I've added these to the DAH2 cheat page. http://www.absolute-playstation.com/ps2/playstation2-cheat-codes/destroy-all-humans-2-cheats.htm
They'll be up there shortly.

Have fun!