Okay I am still lobbing soft balls up here - just been too busy (and too lazy) to get to the meaty favorites (church, museum, piazza, etc.) things. Today I am sticking with wine. I already mentioned Le volpi e l'uva as my favorite wine bar, and while they are also an enoteca, and their wines are usually both very good and great values, the overall selection is a little limited.
For favorite enoteca overall I am going to go with Enoteca Bonatti, a family run shop just outside the center past Piazza Beccaria. They have a great selection in a broad price range, imported wines, Champagne, and offer free tastings in the warmer months, and home delivery. The staff is very friendly and knowledgeable and there are hundreds of wines to choose from.
A close runner up is Enoteca Millesimi - I would go there more often but the majority of wines there are a bit out of my budget. Millesimi also has a superb selection of French wine and Champagnes, probably the best in Florence if not all of Tuscany. In either case you can't go wrong though if you are looking for great wine.