I just upgraded to Ubuntu 14.10 (from 14.04). When I unplug my external monitor (I'm on a laptop so this happens often) the mouse gets a second pointer just below the normal one but rotated 90° counter-clockwise. I think the rotation is due to the external monitor also being rotated 90° counter-clockwise. The double mouse pointer sometimes goes away if I restart gnome-shell, but often stays.
Here's a photo of the result (a screenshot wouldn't capture the pointer): http://imgur.com/Qt71709