you won't be allowed into the secret trackball society.
We have our own handshake/grip... monthly meetings.
Urebel_scum is our Grand Poombah! (he has to where a viking hat or fez when running the meetings)
I think i've said too much.. i'm gonna get blackballed =P (no pun intended)
Rampy
LOL. Rampy, we had to call a secret meeting with the only thing on the agenda was to vote you out or not. Lucky for you, we were too busy playing marble madness, golden tee, cabal, centi/milli-ped, missile command and the rest of the ~100 trackball games to vote, so you're still in.

But on to the original question:
Besides the one hundred trackball games (many of the best already listed in the prior linked thread and here), and windows navigation, analog joystick games do pretty well with a trackball in mame. In fact, mame32 lists analog joystick games in the "trackball" games folder.
On the same line, if you don't have a spinner, a trackball is the next best thing. Again, mame32 lists spinner games in the "trackball" games folder.
So it you don't have an analog joystick or star wars yoke on your control panel, a trackball is great for most "AD_stick" games, including Star Wars, Empire Strikes Back, and Space Harrier to name a
very few. And if you don't have a spinner, there's tempest & arkanoid just to name only a couple.