Here's what I use:
CODE
enum Buttons {
BUTTON_UP, BUTTON_UPLEFT, BUTTON_LEFT,
BUTTON_DOWNLEFT, BUTTON_DOWN,
BUTTON_DOWNRIGHT, BUTTON_RIGHT,
BUTTON_UPRIGHT, BUTTON_START, BUTTON_SELECT,
BUTTON_L, BUTTON_R, BUTTON_A, BUTTON_B,
BUTTON_X, BUTTON_Y, BUTTON_VOLUP...