We present a study of user performance in a First Person Shooter game comparing a prototype trackball controller, a standard game controller, and a keyboard and mouse. The prototype controller replaces the right analog stick of a standard game controller (used for pointing and camera control) with a trackball. To measure the performance of the three input devices, participants played two games. Penguin Hunt measured the number of target hits per minute, which was 28.1 with the keyboard and mouse, 22.9 with the trackball controller, and 21.7 with the standard controller. Modern Warfare measured average completion times, which were 26.8 s with the keyboard and mouse, 31.8 s with the trackball controller and 35.5 s with the standard controller. The trackball controller represents a 5.5% target hits increase over the standard controller in Penguin Hunt, and a 10.4% speed-up in trial completion time in Modern Warfare.