Show & Hide bars
Almost all pop-ups do hide the bars (menu, status, etc). Most of the time this is wanted by the user, so disabling this feature completely in the Javascripts-Settings menu isn't advisable. But sometimes having the menu available in a pop-up is necessary. So integrating a "view bars" command in the right-click menu would be handy.
Minimize to tray
I know there is an extension that does exactly this, but the extension often doesn't get updated if a new Firefox version comes out and so has to be disabled due to incompatibility (as is the case currently with Fx 1.5)