As a personal request from myself back in January of this year in a "hack" forum (on the other website), the Atari 2600 verison of Centipede has been hacked to work with an Atari CX-22 trak-ball!!
It is only in NTSC and only works with the CX-22 trak-ball and NOT with the CX-80 trak-ball.
Hack made possible by Thomas Jentzsch & Omegamatrix. Here's the details:
Success! At least for some of you. Attached you find a trackball version of Centipede. This only works for the CX-22.