gnome-panel
This should make both the top and bottom Gnome panels show up - you can delete one of them and/or move them wherever you want (top, bottom, right) and further tweak them so they don't interfere with the way Unity looks/behaves.
In my screenshot I've only kept the top panel which is set to autohide and "Expand" is unchecked. That means that my panel (which only holds one applet) will automatically hide and it will only take a few pixels of the top Unity panel when I need it.
Using a Gnome panel also means you'll get the ALT + F2 Run dialog back (nothing happens when you press ALT + F2 in the default Unity setup).