@Laser
A mouse can have 3 buttons using pin5 for middle mousebutton. Joysticks/pads usualy doesn't have this pin connected but there's nothing stopping you from connecting it aswell and then you have a 3rd fire input. As for what software support this 3rd button... well... not much but that wasn't the question now was it? If it's there, use it!
Anyone know how to make an analouge joystick work as if it was a mouse?