Well I made this for videos and thought people might like it. It is a NES zapper and I added two red led's and a 12v battery and a 100ohm resistor.
Tools:
Screwdriver
Soldering iron
pliers

Step 1: Taking It Apart

Ok so with your tools in front of you lets start. take all the screws out and take the covers off and place them to the side. Remove the weights and take the 3 main screws holding the trigger assembly on. Do not take the trigger assembly apart. desolder the connections from the assembly.

Step 2: Add the Leds and Battery

Put two led's you can put more but I only had two bundle them together and add a 100ohm resistor then e tape them up. and add two leads. And solder one of the leads to the switch then add a wire to the switch to the proper terminal of the battery. And the other lead directly to the battery. Put the battery where the weight goes you may need to break some plastic to make it fit.