Modanung :o No, I didn't try that!
(In no particular order.)
(Honorary mention: GL-117, a true classic.)
My favourite libre games are Freedoom, Avoision, Adventures on Planet Zephulor, Which Way Is Up, Pingus, Dave Gnukuem, Heroine Dusk, Trackballs, Me and My Shadow, XEvil, 0 A.D., Duckmaze, Orbit-Hopper and Xonotic.
Only libre assets makes it a bit harder. I tried to think of some less commonly mentioned ones aside from Veloren.
Alchemy Quest (or Open Alchemist)
Angband (without sound unfortunately)
@dulsi Silent Angband or it doesn't count. ;)
Cendric seems to have unfree assets as well.
@Technopeasant That's not how you count to five! More like schfifty-five.
Modanung Sorry about that I didn't go back and check Cendric. Also didn't realize Angband sounds had a problem. Added Inertia Blast as a replacement for Cendric.
Fine, if you insist. 😛
...let me demonstrate once more:
EDIT: Frets of Fire needs a default free culture music pack. Licks of Liberty?
Ok. Since there weren't any more answers for a while, let me summarize: If I list all games mentioned more than one time I get the following list:
The Fab 5 of libre gaming:
(In no particular order)
Edit: I personally think Pingus isn't so popular.
Peter I personally think Pingus isn't so popular.
Actually, it was pretty high-ranking on Ubuntu Software Center for a period of time, and it still retains a 4-star rating.
forty_sham Well then it belongs righteously into the list.
It was also the first Game of the Month selected for work on The Linux Game Tome back in 2003.
Seems like a fairly good and varied list.
My top five would be: