I live in Oak Creek, but whenever I'm on the east side I have to stop in at Koppa's. This is a neighborhood grocery, deli, liquor store and gourmet foods shop all rolled into one super Mom & Pop operation (I just adore the Mom & Pop shops!). The prices are a bit higher than you'll find at most groceries, but the ambience, service and selection of unique items is well worth it. There's often a bit of kitsch thrown in as well, with humorous signs and t-shirts.
PROS: Family owned, gourmet selection