These are the FLOSS games that stand out, list your own favourites or most-play games.
--//--
I would rate all of these, as worth a try:
Shattered Pixel Dungeon
Cube2:Sauerbraten
SGT-Puzzles
Andor's Trail
AssaultCube
Minetest
Neverball/Neverputt
PowderToy
0ad
Fillets-ng
Anuto TD
Xmoto/Bloboats
Flightgear
Kobo Deluxe
Enigma (oxyd)
LiquidWar5
H-Craft Championship
Numpty Physics
Wesnoth
The Dark mod
Have completed SuperTuxKart, BlobWars 1&2, Flare, Frozen Bubble, Hex-a-Hop, Holotz's Castle, SearchAndRescue II, Alex the Alligator, Project:Starfighter, Stormbaan Coureur, Trigger, all are fun.
--==--
Can find details about most of the above games here:
https://libregamewiki.org/List_of_games
FLOSS gaming is excellent, thanks to all these devs and asset creators.
--++--
BONUS TOMT:
I'm looking for the name of a FLOSS Quake1-mod, puzzle game, that was about placing gravity points, to curve a stream of particles around the level, and eventually into the goal target. (May have used irrlicht)
If anyone knows the name of this one, please let me know, it is my white-whale of games.
Both naev and endless sky will scratch the top down space trader itch.
I killed a lot of hours on the official release of endless sky, it was nice to see it unexpectedly in the arch repo.
I tried Naev before and it looks very polished.
A little too involved for me, the whole star-trading style. I never got into Elite during the Amiga/ST years, but I get how polished and layered Naev and Endless Sky are.
Get into it people, if those are your type of games!