I'm developing a full screen app that I just launched that has apparently completely stolen the keyboard to the point where nothing can get me out. Not command-option-esc, not command-option-shift-esc, not command-tab, nothing. Moving the mouse to the edge of the screen doesn't bring anything up. Can someone help me before I just force shutdown?
If you have an Apple keyboard, you could try using one of the function keys that brings up Mission Control or shows the desktop — typically F3 or F4, but it may vary depending on the vintage of keyboard (it may be fn-F3/F4/etc. depending on your system preferences).
If that doesn't work, try bringing up the shutdown dialog with either the power button or ctrl-eject. That might be enough to release keyboard control and allow you to command-tab out. At the very least you should be able to perform a clean shut down.
Finally, if you happen to have Remote Login enabled (in Sharing Preferences), you could SSH in from another machine and kill the errant process.