Definitely bring shoes with which you are comfortable for walking. Often, the roads are steep and often they have cobblestones. Your feet will be grateful in the evening. Bring warm clothes, even in summer, as the temperature in the valleys might get colder than at the coast. Umbrella or raincoat might be a good idea, depending on the season. I needed good rainprotection in April (2008). If you want to visit churches, bring something to cover arms and legs, as you might not be let in with unappropriate clothes.
There are enough pharmacies where you can get medical supply. Bring translation for prescriptions. You might like to bring first aid kits with band-aid, as you might have blisters from walking. Foot cream is a good idea, too. My feet were happy in the evening with this :-)
The most magic impressions throughout whole Umbria are the churches and other buildings. Many of them have ornaments, sculptures and other details where you would need a good tele lens.
There is no beach in Umbria, but depending on the places you stay, you might have access to a pool. Or you might like to swim in one of the lakes (Trasimeno, Piediluco, Bolsena). If you plan to hike, bring all your equipment, as it is most unlikely to find places where you can rent tents and the other stuff.
Binoculars are a good idea, for wildlife watching or looking at the building details. Maybe a torch as well, as depending where you go, streets might not be lit appropriately. Italian dictionary is also a good idea.
