Hide dock bar permanently

To make the Dock instantly leap back into view when it’s needed, rather than slide, open a Terminal window and type the following:

defaults write com.apple.dock autohide-time-modifier -int 0;killall Dock

I find this useful, but if you’d like the animation for the dock to reappear to last for a split-second, try the following:

defaults write com.apple.dock autohide-time-modifier -float 0.15;killall Dock

To explain, changing "0.15" with any number can let you tailor things as it represents the time in seconds taken for the dock to reappear fully.

To revert back to the default sliding effect, open a Terminal window and type the following:

defaults delete com.apple.dock autohide-time-modifier;killall Dock

The plist edit should work with Signed Apps, you just might need to force a resign. Try the command sudo codesign -f -s - /path_to_app/appname.app, replacing appname with the name of the app you are looking to hide from the dock.

Note that this will also disable menu bar actions, but all keyboard shortcuts should still work.