Malls are really the poster child of this thread, as they tend to harbor multiple of the same store. For example, using the King of Prussia mall, there are...
5 Auntie Anne's counters
3 Sunglass Huts
2 Coach's clothing stores
2 Gamestops
2 Shake Shacks
2 Starbucks
and lastly, 2 Time After Times
Most of these examples are in different areas of the mall (the mall is divided into the Court and the Plaza, so one store in each area), but some of these are literally a floor above/below each other. Two of the Auntie Anne's locations are essentially separated by a short walk and a turn down the hallway. I want to say the Gamestops are visible from each other, but I'll need someone to check me on that.