Hide an application's dock icon
Try editing the app's plist (inside the .app package i.e xScope.app/Contents/Info.plist)

and add or edit the following entry:

&lt;key&gt;NSUIElement&lt;/key&gt;
&lt;string&gt;1&lt;/string&gt;


Because this hides the menu bars, it should be possible to create a keyboard shortcut in System Preferences&gt;Keyboard&gt;Keyboard Shortcuts for any functionality that you need the menus for.