Well, think about it this way.
Hunter-gatherers settle into villages and towns when agriculture produces a better yield than hunting and gathering. Lots of inventions at that point are about feeding yourself and/or your community -- writing, wheels, roads, plows, horse collars, etc. Anything that produces food/drink, processes it, or sends it on its way are going to be of great use to any society. These items may be used indirectly to this purpose. A Decanter of Endless Water or three allows a nation to grow crops on otherwise marginal land, for example.
Agriculture allows folks to specialize into craftsmen, priests, warriors, etc. Magical tools and weapons are going to be big on the list.
With nations and empires, you need to project power. The easiest way for the Romans to do this was to build a massive network of roads. D&D civs have magic portals for the same purpose. Portals are also safer, because you can turn them OFF. Anybody can use a road.
Keeping order in a large society requires laws, courts, and police. Mercy weapons that do nonlethal damage, gems of true seeing, zones of truth, etc., will all be hugely useful.
People have already touched on the whole construction capabilities. Keep in mind that one of the reasons to build huge monuments and such is to KEEP PEOPLE EMPLOYED. Instead of works getting done faster, some of them will just become more amazing and grandiose in scope. Fast construction will be reserved for fortresses and such.
Any medical technology will be critical. Human societies in the real world have been periodically ravaged by plague, typhus, small pox, and other diseases. Some societies have been wiped out completely. A Wand of Cure Disease is enough to change the course of history (just zap the carriers with the wand when the signs first start to show).
Any king or emperor with any sense is going to have a clone, or a ready-to-go resurrection option. Even in lower-magic areas, raise dead is only a 5th-level spell. Any assassin will have some option for trapping the target's soul, or at least destroying a body. Otherwise, death is just an inconvenience.
I think the best way to develop a unique feel is to try and think through the nuances of magic, rather than just apeing modern inventions in a medieval setting. Modern technology has a number of limitations (conservation of energy, square-cube law, limitations of materials, speed of light) that magic does not have. Don't create an imp-powered vacuum cleaner...create a room that disintegrates anything smaller than 1/8 inch that hits the floor.