Toggling Dock with Shortcut only? - NOT automatically with mouse...

Try COMMAND-OPTION-D. If that doesn't work then open Keyboard preferences, click on the Shortcuts tab. I believe you can then set up a shortcut for the Dock.

One problem with this is that the F12 key is reserved to activate Dashboard. In order to use it to show/hide the Dock you would first need to use other shortcuts for Dashboard. Presently F11 and F12 are reserved for Expose and Dashboard.

If COMMAND-OPTION-D work to toggle the Dock then you can either try a different shortcut (one that isn't required already for something else) or you can use a third-party utility to program a keyboard macro to which you can assign the keystrokes that toggle the Dock.

The current list of built-in keyboard shortcuts can be found here: Mac OS X keyboard shortcuts.

Keyboard macro utilities can be found at VersionTracker or MacUpdate. QuicKeys or iKeys are widely used utilities.

AFAIK, this is impossible. Kappy provided you with a keyboard shortcut but that won't stop the dock from showing up when it's hidden and you mouse over the bottom of the screen.

Ok it seams that nobody reads your question so I will try to answer it.
There is an solution for your request: http://www.old-jewel.com/dockgone/

If your are technical enough there is an detailed guide in how to hide stuff in your finder. It is a little old but I think most of the stuff still works:
http://developer.apple.com/technotes/tn2002/tn2062.html

this might be a nice feature to have. you can leave apple a feature request here:
http://www.apple.com/feedback/macosx.html