Rock Band has easily become one of my favorite games, which I tend to play a lot. I'll switch out between rocking the guitar, drums and vocals, however, I feel bad that those without full use of their legs can't use the drums. Thankfully someone has created an awesome mod that will allow anyone to play the drums, so long as they have full use of their hands and arms.
The drum unit consists of four pads and a pedal. For around $20 and a little work, you can remove the pedal requirement and replace it with an additional button located on one of the drumsticks. All you're going to need is a doorbell, an audio Y-cable (35mm to RCA) and a few tools. You'll simply cut off the ends of the Y-cable (not the 35mm end), then strip a little wire back from the exposed ends, wrap it around the two screws on the inside of the doorbell and mount the doorbell to your drumstick.
This will take only a minimal amount of work to do, and should create an alternative way for those with disabilities to rock. The hardest part is going to be learning to coordinate the button presses with your drumming. Then again the same goes for those using the pedal.