In the world of sandwiches an "Amighetti's Special' is second to none. I grew up on The Hill in St. Louis. I have since lived in many, many other cities, but Amigetti's is always first in my book for sandwiches. Its always a "must eat" place when I return to St. Louis. Its fairly close to south St. Louis attractions like Forest Park and the Zoo, so if you're there on Vacation it would be easy to work in.
Pros: Inexpensive, Fantastic Food, Quick Service
Cons: Parking can be hard, Can be crowded