I still play Elona and several flavors of Angband.

Greatly improved by community contributions.

OpenTyrian

I'm a simple girl:

• LTris
• LBreakoutHD
• Gweled
• Frozen Bubble
• Gnome Mahjongg
• Gnome Tetravex

Too bad there isn't a single good linux pacman around...

Open Hexagon

Apotris is an excellent famous-block-stacking-game clone for the GBA (and other platforms), it has a version for Portmaster that will run on many if not all Linux handhelds like the RG35XX and similar, but will also run in any GBA emulator.

From fdroid, Feudal Tactics and Antimine.

Andor's Trail - RPG where you search for your missing brother. Still under development, but there's a lot of content. It's convenient to fill a few spare minutes or waste hours.

Minetest and Widelands

Only AAA games on these premises, cause I ain’t no stingy bitch

Technically Urban Terror isn't open source, but the Quake3 engine it runs on is.