Winning a game of NONO is a fun little puzzle game [video]. It is built on top of LÖVE, which is fairly easy to have for Win and Lin users. Mac builders wanted!
I found a list of open source games for the Mobile Edition of Java. About 25 puzzle/arcade titles, mostly GPL'ed.
The Apricot project is ripening with great speed! Further additions to blender have been made and videos of a playable prototype recorded and uploaded. The plan to unleash "real Open Source power" by opening Apricot's code repository has unfortunately not been fulfilled yet.
The opinion exists, that a game will be less fun for people who were able to play a development version of it. I don't think this problem is a big one and believe that simply because of the necessity for compiling, most people will wait for an official release.
An example of a story-based single-player game with an open Subversion repository is Rastullahs Lockenpracht, a TDE-based 3D RPG. I haven't tried it so far because the last time it caught my attention, compiling code was a large burden for me. Now I won't try it as it appears to be depending on non-free Nvidia and Fmod libraries.
It seems that the Apricot team has the same problems that I have when recording with recordMyDesktop: The recorded field doesn't fit the selected window, which results in capturing of unwanted space above and below the targeted window.
Warsow's developers started accepting donations. They want to use it for making participation in an own LAN party cheaper. I'm becoming more and more uncertain about the ultimate goal of the project. Is it profit? A fun game? An elitist community? Being popular? PS: What I'm talking about here is the "ultimate master plan" - which I'm certain every open source project secretly has. ;)