For those who aren't from the Boston area, I should mention that what the rest of the U.S. calls a milkshake, we call a frappe. (Here, a milkshake is milk and syrup, blended or shaken until frothy.)
Anyway, at the local ice cream shop, Colleen's, they have Brigham's ice cream (a local brand that's quite good for packaged ice cream). Two of my favorite flavors are Oreo and Peppermint Stick. Since chocolate and peppermint go together nicely, I decided one day to try the two flavors together in a frappe. Since then, if I'm at Colleen's and in the mood for a frappe, it's the one I always order. Rich, creamy, chocolaty-minty goodness that you can drink with a straw (though sometimes chunks of Oreo block it up). Summertime refreshment at its best.