This is a quick hack/mod to a arcade button that allows illumination via a single LED.

Equipment:
Drill,
arcade button (see http://www.sparkfun.com/products/9340)
and a super bright LED (see http://www.sparkfun.com/products/531)

Step 1: Remove the Switch

1.) Gently pull the longest tab out of the switch
2.) the switch should now easily "flip up"
3.) you can remove it from the button

Step 2: Remove the Inner Cylinder and the Spring

1.) push the tabs towards the center as shown in picture
2.) you should now be able to push the tabs through the holes allowing the inner cylinder to fall out
3.) this pic shows the disassembled button

Step 3: Drill the Hole and Mount the LED

1.) drill a hole in the bottom of the button as shown in the picture
2.) install the LED (you can use a little bit of super glue or a glue gun to keep the led in place
3.) bend the wires around one of the switch supports (see pics)
4.) reinstall the switch

You could mess around with some color LED's or even a different voltage to play with the brightness. I used an Arduino board to switch the LED off or on depending on when the buttons were pressed, the possibilities are endless..... enjoy!!