free games to install on ubuntu

[mahesh]

so far I have installed shareware doom

I installed flightgear

I installed gnuchess
along with xboard to have gui to play against the computer

Everybody says Team Fortress 2 is one of the best free games, but I was wondering if anybody has things that can be installed with sudo that are worth checking out.

Torrents seem too much like stealing, but what does an emulator hurt?

Any recommendations for freebies that are out there?