What kind of game? For mmorpg, realm crafter looks like the best (only?) one.
For more general game development theres:
http://www.garagegames.com/ 2d and 3d, lots of "indie" games have been made with this. Some even for xbox 360 and wii.
http://www.crystalspace3d.org free and open source 3d engine
http://en.wikipedia.org/wiki/Action_ScriptFor making flash games like those found in the fiesta fan arcade.
I know there are more, but thats about all I can think of right now.