For a quick float, I like Bryers French Vanilla floated in Coke, with a bit of maraschino cherry juice added, and a cherry on top.

But I prefer a milk shake to a float. my favorite is butter pecan ice cream, a bit of whole milk, some ahersheys chocolate syrup (preferably canned, it has a different flavor than the plastic bottled), and a splash of maraschino cherry juice. Yum!