You want the best kielbasa? you need to go to Franks Market in Grand Rapids. The best loaf of sourdough in town? Sarkozy's Bakery. If you're up for a drive then Zingerman's in Ann Arbor is probably worth the pilgrimage (but stretches the 'local' part for me). Is pizza your thing? Chicago Style Pizza is the best I've had outside of Chi town.
Where do the food gods demand you go locally for the very best [fill in the food item]?