Ok we've been to Italy many times and driven alot but what we haven't done is tried a one day rental out of Florence. What is the least expensive car rental in Florence.

When I did a one day rental from florence for a wine tour the cheapest was auto europa.Which believe it or not is a different company than Auto europe,which did not rent for one day as of 2004.
I highly recommend the super cover plus insurance.A nice car the Alfa 147 is about 100 dollars for one day with full coverage.there are very small cars for cheaper.The town location is near the train station and is not too bad to get out of town from there RR

I just did a two day class B (manual) rental through Auto Europe for $78, the company was Auto Europa on Borgo Ognissanti, as Robert notes, not too far from the train station.