Green laser locations
Green lasers will allow enemies to be killed with a single shot. They can be found at the following locations.
Andy's House
When you go to the garage, find a way to get up to the van. When you get to the top, you will see a green laser.
Alleys and Gullies
Turn to the right when you see the first airplane box.
Andy's Neighborhood
Find your way to the location with a broken car. The green laser should be right in front of you.
Level select
At the options screen, press Right, Left, Circle, Triangle(2) to unlock all levels.
Replenish Health
When your health is gone, quickly exit the level then return to it and you should be invincible.
Debug Mode
At the title screen press X, circle, square.