When an object is selected in the inventory, a pop-up window "previews" it. This could form the basis for many extended features - a way around opening packages without leaving prim-junk on the ground, a way of previewing what's at a landmark, so you can choose whether to go there or not, a way of seeing how an item of clothing might look when mixed with what else you are wearing... but none of those can even begin to be thought of without an inventory preview.
Making the object in the preview pane spinnable and zoomable would be nice too - all too often, a vendor's description of an object you can't modify is pithy or irrelevant to how you want to use it: being able to see it "in preview" is much more useful.
In fact if I am really pushing the boat out, I'd like the preview pane to include the option of a personal notepad for every object, so stuff that's no-mod no-whatever can still be annotated.