For more cool projects, visit my youtube page: http://www.youtube.com/channel/UCksEFn8xaLP0z4rsiHa9zcA?feature=mhee
To begin with, you are going to need a ton of disposable cameras. Depending on how powerful you would like your ray gun to be, you will choose how many disposable cameras (though at a sufficient amount there is a ceiling to how much the pistol can pump out). Politely go to a nearby photo developing store and ask if they have any used disposable cameras.
From my experience, the store employees' willingness to cooperate is dependent on a few things:
1.) How old you look
2.) How much you look like you know what you are doing
3.) How dangerous your project sounds when they ask you what you need the cameras for
Once you have a big bag full of cameras, its time to start shucking! Inside each camera there are many useful components we will need. But before removing the outer plastic container, you must first remove the camera's battery, and have a thick piece of metal insulated from your hand. Use this to discharge the camera's capacitor very carefully by tapping the two pieces of metal jutting out from it. Once the capacitor is discharged and the battery is removed, the electronics are safe to touch. Remove them. I have attached a photo with the basic information on it. Though there are many different designs for disposable camera circuits, they all work similarly.