Abben's List of Very Good Free Open Source Games

This is an opinionated, human curated list. Games listed here tend to have some combination of the following qualities:

- Light on system resources
- Works on Linux
- Replayable
- Fun to play (sorry 90% of Linux/Tux games)
- Has this quality

I will add to this as worthy entrants emerge. 

Cataclysm: Dark Days Ahead
MineTest
Liero
C-Dogs

Better lists:
Wiki: List of Game Engine Recreations
Wiki: List of Open Source Video Games