San Gimignano is a wonderful little Village but it is full of little shops. The outdoor cafe near the Museum of Torchure was a great lunch stop and there was Gelato across the way. If you've seen the photo of the Leaning Tower, you've been to Pisa - it's crowded, and not the safest place in Italy.
But, if you've never been to Florence, that would be my pick. You need a minimum of two or three days for Florence, but you must see the Arno River, The Stature of David...I could make a long list. Love Florence. Can't wait to go back. Even for a day off the ship.