- graphical programs (but Blender makes a heavy use of hotkeys) - some games - new interfaces. Mouse is easier to use initially. Websites fall into this category, I'd say they're even a pathological case: it's pretty common for a website to radically change its interface. It can be partially dealt with, for example Konqueror used to display link hotkeys when you press CTRL. I need to look it up.
Most of the time you don't require extra precision a mouse offers. A button press is binary, so why require precise movements, mess with icon sizes, etc ?