How do you break free of a fullscreen app on Mac OS X?
There are some, mostly games, that when they become unresponsive won't allow you to switch to another app with Command-Tab, and I know no other way to close that app or get away from it. Command-W or Command-Q won't work either.
Is there a shortcut to launch Activity Monitor, or Terminal, to kill the application?
cmd+alt+esc then Force Quit the offending application.
Sometimes cmd+enter will put it in “window mode”.
Shift+Option+Command+Escape, when held down for three seconds, should force-kill the active application in Mac OS X, similar to ending an unresponsive task in windows.
First, try hitting esc. That'll make well behaved programs such as DVD Player or VLC exit Full Screen Mode.
No luck there, try command+tab and see if you can cycle to another open program or the Finder. ( OP tried this, but just adding for completion's sake )
Then try option+command+esc next, to try and Force Quit the application.
If none of that works...you could try to ssh into the machine and kill the offending process via Terminal..
That'd be all I try before rebooting the Mac...
in many cases, cmd-m is often the key sequence to toggle full screen mode...
To exit Mac OS X Mountain Lion application full screen mode:
In OS X 8.2, an app in full screen mode will display the now hidden application menu by moving the cursor to the top of the screen. At the far right of the menu appears a blue background arrows version of the "full screen" icon (with the diagonal arrows) that you used to initiate the app to full screen mode. Select that to toggle out of full screen mode.
In Xcode, you exit fullscreen mode by holding the cursor at the top of the screen. This makes the menubar appear, allowing you to toggle the fullscreen button. (confirmed in Xcode 5.1)
Games will usually run under different settings than your desktop (with 3d and stuff) - changing between those different modes can be taxing on the computer, and making it unresponsive is common, but it SHOULD eventually switch after a few seconds.
one way to make the switching faster is to run the games under "windowed-fullscreen" mode rather than "fullscreen" - this make them run with the same configuration as the desktop, albeit with a performance penalty.