Play As An Alien Kronnhunter
Right when you start the game, shoot nothing else but the first three Staar Team members you see. The game will restart and you will now be playing as a Kronnhunter.

To become a Kronn Hunter (an alien, rather than a human):
In the "Beginning" level, shoot the first three S.T.A.R.R. agents without reloading or shooting anything else

Use the controller rather than the gun:
at the pause screen, enter this code: Triangle, Square, Triangle, Left, R1.