The Atari Jaguar CD is an add-on for the Jaguar. It was too little, too late for it to do anything for the doomed system and its doomed maker. Little over a dozen games were released for it, most of them also available on other systems. Notorious for its frailty, good luck finding one in working condition. So, not really worth getting.
Alice's Mom's Rescue
A cute homebrew (but commercial) retro puzzle platformer, vaguely inspired by "Alice in Wonderland". A little girl has to traverse huge maze-ish levels and rescue her mommy from the giant raven. Magical mushrooms allow her to trip balls change size to reach different areas. Windows version is included in the same disc.
While Cybermorph, the Jag's original pack-in cartridge, was not very well received, this CD sequel is a much better game. The framerate was increased, the annoying scenery pop-up was greatly smoothed, the worlds are better designed, and now there is — oh joy — some music during the game.
Iron Soldier 2
A pretty cool mech game with very destructible environments. It actually looks cool when a building is blasted into a bunch of polygon cubes. Perhaps a bit aged now, but it runs smoothly, and that's more than you can say about many Jaguar games. Also released as a limited edition cartridge.
World Tour Racing
WTR is no masterpiece, but it is a competent and perfectly playable racer — and that is reason enough to call it a huge improvement over atrocities like Checkered Flag and Club Drive.