Easy. Start off at Gov't Center and walk down to the North End - this will take you through a couple great wind tunnels in the blistering cold. Have a late lunch/early dinner at La Famiglia Spagnuolo's. This way you're probably timing it so that your date is starving, and you're taking them to one of the lowest rated restaurants in the state to boot. Suggest the Aquarium as an after-meal activity, but then refuse to enter it and just look at the seals outside. Bonus points if you can get a water taxi to drive you around in the frigid wastes of the harbor afterwards.