GUI stands for Graphical User Interface. It is widely pronounced "goo-ey"; I even do this myself despite the fact that I absolutely hate the twee cuteness of it all. It's just become so deeply ingrained that you don't have any choice. Anyway...
An InsaneGui is one with a behaviour which could under no circumstances be of use to man or beast. There is a further level of insanity, which is a PathologicalGui. This is which as well as being no help to anyone, under any circumstances, could only succeed in being a hinderance to everyone, under all circumstances.
I never really got happy with Gui's. They never really really worked well for me, because I seem to find InsaneGuis often. At first, I thought that this was a curse, but now I realise that it's a gift, and one that I should share with the world.
I'm am largely going to ignore the concept of the IrritatingGui. I figure anyone reading this (I accept that this is unlikely), will already have plenty of these for themselves.
To start out even handed, I am going to describe both an piece of Microsoft and a piece of Apple insanity. These are the OutlookStartDatePathologicalGui and the ItunesTrackOrderInsaneGui.