IMHO Marble Madness is a must. Other ideas:
Cabal (one of the sets is for trackballs)
Rampart (Trackball)
Centipede
Discs of Tron
Any of the good golf games like the Golden Tee series.
Any of the good bowling games like World Class Bowling.
Lemmings, if you happen to find the port funny.
There are also some shoot-em-ups which make use of the trackball, but can't quite remember any. Bermuda Triangle, maybe. I'm sure there are others. Try to browse MAWS by control, it will give you more ideas.