If you're Target expeditions are like mine, you're looking for inexpensive portable nibbles, so I wouldn't steer you towards a nice sit-down place. But there are plenty of great little finds all around Target--Cake Man Raven for one, but he often runs out of cake.
Going toward the slope, one of my favorite sandwiches in the city--hot and toasted turkey and swiss with an assortment of condiments--is at City Sub on Bergen right near 5th Ave. I might wander on down Fifth Ave, to the Chocolate Room and Gorilla Coffee, pick up a pound of fresh beans. You could also continue on down to Beirkraft and get some interesting beers and cheeses and chocolates.
86 5th Ave, Brooklyn, NY 11217
191 5th Ave, Brooklyn, NY 11217
264 41st St, Brooklyn, NY
Around the corner, you're in prime Fort Greene. Try Smoke Joint on So. Elliot between Fulton and Lafayette (http://nymag.com/listings/restaurant/...) or their sandwich/salad takeout business next door, Lil' Pig. Also, Burger 67 is across the street on Lafayette. My favorite is the Southwestern: chipotle aioli, roasted peppers, jack cheese with scallions. Also, on your way back to the train, stop by Cake Man Raven for a slice of red velvet cake. Personally, I like the version made by Betty Bakery on Atlantic Avenue better, but Cake Man started it all and many still swear by it.