***Disclaimer: I am not liable for any damage that may be caused to your property or self from following the instructions in this tutorial. Soldering irons can be very hot and cause burns, as well as possibly break your Xbox 360 controller. Opening your controller's shell will void its warranty. If you are unfamiliar with soldering I suggest you acquire some practice on blank boards before attempting this mod, as the LEDs are quite small. ***
Step 1: Supplies
Soldering Iron: Your generic 10-15 Watt Radioshack soldering iron, available for about $15. Though not necessary, for small projects like this I take a metal file and sharpen my soldering iron to a fine point. It will make the install much easier.
Silver Rosin Solder: Also available at Radioshack, silver solder more evenly distributes heat, and rosin creates a clean bond between two metals. Around $3.
Copper Desoldering Braid: This thin wire braid will absorb solder when placed inbetween the soldering iron and a terminal that needs to be cleaned. Necessary to create a flat base for the LED to sit on, makes the install much easier and can fix mistakes. $3.
Xbox 360 Wireless/Wired Controller: Microsoft controllers are available at any store that sells video game equipment. Retails for $50.
SMD 0603 LEDs: You can select whatever colors you wish for this mod, this instructable uses four blue 0603s. I would encourage you to purchase the brightest mcd rating you can find, the difference between a dim (120mcd) and a bright (400mcd) 0603 is around 10 cents per LED and worth the extra cost. Though you will only need four for this mod, purchase 8-10, these lights are so small you are going to lose some no matter how careful you are. Here are my recommendations from unique-leds.com
Red 500mcd, $0.33/LED (800mcd are available on eBay).
Yellow/Amber 130mcd, $0.22/LED (350mcd are available on eBay)
Blue 380mcd, $0.34/LED (800mcd are available on eBay).
Green 200mcd, $0.39/LED (1000mcd are available on eBay).
White 800mcd, $0.38/LED (2500mcd are available on eBay).
My favorite eBay sellers for LEDs are HKJE LED Lamp Center and Light of Victory Hi-Tech LED Store.
Security Torx T8H: Xbox 360 controllers have security screws, meaning there is a pin sticking out of the center of the screw that prevents a normal T8 Torx from fitting in. If you are cheap or don't want to wait, get an awl or a very small flathead screwdriver, and crack off the pin with a good whack from a hammer, letting you then use a normal Torx driver. I suggest purchasing your T8H screwdriver from Llamma.org. High Quality $7.99 and Low Quality $2.48
Tweezers: Absolutely necessary to hold the very small SMD 0603s. Try to purchase tweezers with the flattest edge you can find, round endings will cause the LED to shoot outward when you tighten around it. Around $3-5 at any local store like Walgreens.