Plan9 comes with some games in /bin/games like sokoban and sudoku, but the interesting stuff is mostly in the Contrib directory.
A non exhaustive list includes:
There are quite a few go games out there:
- paurea has a little goban at /n/sources/contrib/paurea/goban/
- gnugo-3.6 has been ported by andrey /n/sources/contrib/paurea/goban/gnugo-3.6.tgz (needs gcc)