LED Buttons
Several online retailers provide lighted LED buttons that you can purchase and install in your XBOX controller, in place of the default buttons. Typically, you can replace the four buttons -- X, Y, A and B -- on the right of your controller as well as the center XBox button and the surrounding "Start" and "Select" buttons" to light. While this can increase aesthetics, it can also help you to better see the buttons in the dark.
Paint
Painting the exterior of your XBox 360 controller may be more appealing if you're not electronically inclined. You can remove the back- and face-plates to paint them. You may consider a feathered paint job, where one color gradates to another with a feathery texture, a basic gradation, an allover paint job or even use a stencil to add special shapes or designs to your controller.
Rapid-Fire
The rapid-fire modification or hack is one that forces your controller to think that you are firing more quickly than you actually are. In games such as Call of Duty and Halo, this allows you to more quickly fire at the enemy and potentially cause more damage or take down more enemies in a shorter time frame than normal after you activate rapid-fire mode. Some kits offer customizable or multiple pre-set modes so you can choose the speed that best fits your needs.
Shell Replacement
Replacing the shell on your XBox controller allows you to change colors and finishes -- from matte to glossy -- without having to paint your original controller shell. You can purchase kits that contain the front and back shell pieces, along with color-coordinated buttons and battery packs. GamerModz sells a line of glossy shell kits while Extreme Mods is another online retailer that offers a variety of duo-toned replacement shells for your controller as well as clear case kits.
Miscellaneous
Some of the other ways that you may consider modifying your XBox controller include remapping the buttons and modifying the LED light around the center button. Remapping kits allow you to change the function of your buttons. This may offer more comfortable play if you're left-handed, because many default keys use the right side of the controller, or if you want your controller to behave like one of a different video game console. You may also replace the circular green LED light around the "XBox" button with an LED light of your choice.