Throughout most of my linux life I have had two desktops installed: Gnome and Openbox. The first for most everyday uses, the second specifically to create a no-nonsense environment for games. Openbox just works better for a lot of wine as well as native inux games – less screen-, keyboard and ressources-hogging etc.
So when I log out of Openbox it’s in order toget back to business. GDM sees it differently: You’re always set to log into the last desktop you logged out of. This is just plain wrong. To set it right I found this Fedora forum post pretty helpful. Here’s how I put it to use to set a default desktop for my user, regardless of what I was last logged in to.