Hello all. This howto will tell you how to start a game right from the sessions menu of GDM. I do this because I run Xgl and compiz, and the performance of games while they are running is pretty ******. What this does is instead of starting a window manager, and then starting a game, you can start the game directly. It's extremly easy to do, saves some memory when playing the game, and makes using Xgl/compiz and gaming on the same box much easier. I'm also a memory *****, and figure, if I can save a few megs by not using a window manager at all, why not?

All you have to do is create a game.desktop entry in /usr/share/xsessions . So for example we'll use quake4.
Open a terminal and go to /usr/share/xsessions
cd /usr/share/xsessions
Use a text editor of your choice and create a quake4.desktop file.

sudo gedit quake4.desktop
Now create the Entry.
[Desktop Entry]
Comment=Start Quake 4 straight
And there we go. Restart GDM
sudo /etc/init.d/gdm restart
and it should appear under sessions.

I Hope this basic howto was at least somewhat usefull. Enjoy