Monona Bait & Ice Cream is the kind of place I imagine my parents and grandparents went to a lot as a kid. Shop is set up right in the guys house and filled with ice cream (UW!) floats, sodas, shakes, malts, sundaes and sandwiches too! (Which by the way are gigantic and delicious!)
Aside from the cold treats, it has all kinds of retro 50's candy to buy. Takes you back to a different age.
If you're coming with kids, which I'm assuming a lot of you are, it's conveniently located across from a park on lake Monona with picnic tables and a playground. The ice cream shop has tables to sit at inside, on a screened in porch or outside.
I come here a lot with the little girl I nanny and the owner always remembers what she likes to eat. It's the little things :)