Animal Crossing: Wild World, if you like Animal Crossing.
Elite Beat Agents, if you like rythm games.
Picross is a great value, if you enjoy the puzzles. 345+ and then some (you can download 20 new ones every two weeks-140 already available.)
There are too many games to recommend. Really depends on taste.
For example, about half of my library(30+) is puzzle-style games.







