I got very annoyed by the
ALT shortcut opening Unity HUD.
It was driving me crazy till I disabled it.
Open System settings.
Click Keyboard settings.
Open Shortcuts tab. Select Key to show the HUD and press
Use the following command to disable Key to show the HUD shortcut.
$ gsettings set org.compiz.integrated show-hud "['']"
You can restore this shortcut using the same command with modified parameter value.
$ gsettings set org.compiz.integrated show-hud "['Alt']"
Simple as that.