Since upgrading to Emacs 24.3 I have been missing ns-toggle-fullscreen. This feauture
has been replaced in newer version of Emacs with native OSX fullscreen.
Needless to say native OSX fullscreen can be painful when you are on multiple monitors and even on single monitor setup I find it unusable.
After searching high and low, I found the magic variable which can make Emacs 24.3 behave like old fashioned full screen. Emacs no longer moves to a new desktop and everything works as expected:
Download nightly version of Emacs from Emacs for OSX and add following to .emacs
(setq ns-use-native-fullscreen nil)
After that, when you use toggle-frame-fullscreen Emacs should be on fullscren but
you should still have access to other monitor and things should be fine and dandy!