So this guy built his own gamepad from the guts of both an Xbox controller and a trackball mouse in order to improve his FPS game. This is an amazing project and I wish there was more than 29 minutes of him talking about it, because the design is utterly brilliant - I love the detail of accessing the trackball from front and back, I bet that results in having phenomenal mouse control. The pad itself looks like something Gravis would have made if they were still around. https://www.youtube.com/watch?v=Ug06dhahqg0
