I have an Atari trackball, but my favorites were always Wico trackballs back in ye olden times. I had one for both the Atari 2600 and the Texas Instruments 99/4A (although the TI one needed an external power supply for some reason). I have even used the incredibly rare Odyssey 2 Wico trackball, albeit at a couple of conventions (playing the also rare game, Power Lords).