WarHacks

Click on Aliens to kill them. The bar at the bottom of the screen is the progress of the wave. Type in a cheat code from: STUN, PIERCE, RAPID, FIRE, to change your fire mode (as unlocked, can see what is available in the pause menu). Type any number of + in the console (once unlocked) to charge your weapon. How these work and when they are unlocked should be clear by the dialogue.

Clarification: The phrase "you have a phaser set to stun", indicates you have a weak weapon, this is different to the STUN cheat code.