I was looking at my usage reports when this question came to mind. I wanted to see what reports everyone was view with the exception of myself (as the admin, I'm all over the place and I don't want my activity to skew the numbers).
I think probably the ctrl/shift functionality is probably good enough for this... I just didn't know if the functionality was available anywhere.
From a use case perspective, I don't have any that my users are specifically asking for right now. Maybe someone else has come across a use case. I thought it could come up at some point, so I figured I'd ask. I could imagine wanting to look at all cost centers except a certain one... for example, we dump all our maintenance costs into one cost center... if I wanted to view all cost center costs that are not-maintenance related. But here again, ctrl/shift might be good enough for this, though.