Real Mah Jongg is a social game that originated in China thousands of years ago. Four players, named after the four winds, take tiles from a wall in turn. The best tiles are made of ivory and wood; they click pleasantly when you knock them together. Computer Solitaire Mah Jongg (xmahjongg being one of the sillier examples) is nothing like that but it's fun, or it must be, since there are like 300 shareware versions available for Windows. This one is for X11 and it's free.
Gem Drop X is a fast-paced puzzle game where it's your job to clear the screen of gems before they squash you. You're at the bottom, they're at the top, and they keep coming. Gem Drop X is an X-Window game for Unix, directly ported from the original GemDrop for the Atari 8-bit.