Hi. I found good application which can minimize Nexuiz under Linux, with key shortcut (default it is WinKey+Z) No need to use windowed mode and open console. It work for me, but my luck with Linux is bad, so actually i have to use windows. Bu i'm still trying to play from Linux
http://hem.bredband.net/b400150/
I hope it will be useful for you!
Greetings