Extra mouse buttons beyond just Mouse1/2/3 (Left, Right, Middle click) are extremely common in the gaming community. I'd like to see more options in assigning hotkeys to my mouse, and I'm sure I'm not the only one that'd love to simplify some of the hotkey assignments. Especially considering not all keyboards have full anti-ghosting.

For example, I'd love to be able to have my submarine dive (default assigned to Shift+V) and turn to port (A) at the same time. The default layout doesn't allow me to do that, but assigning dive functions to my Mouse4/5 buttons would be huge.