addictive lunix games

What are some linux games that you can play for hours on end? I don't care how lacking in graphics they are as long as they are addictive. Some classics: crack attack, sdljump, kobo deluxe, moon-lander, neverball, wesnoth, x-moto. What do you play when you need to kill time?

solitaire

Breakout
Super breakout

liquidwar

I'm not sure if you find netwalk addictive but I like to play it when waiting for a download or compiling apps. I can do newbie in 22 seconds, normal in 96 seconds nerd in 250 seconds and the one after nerd in 1430 seconds

http://rooster.stanford.edu/~ben/netwalk/

Tremulous or GTFO