Download this app if: you want complete access to NYC public transportation.
NYC Bus & Subway Maps offers something very simple, yet invaluable to both native and tourist alike. Complete offline access to the official MTA Subway and Bus Maps for all five boroughs of New York City. A return to it's original no-frills design, NYC Bus & Subway Maps is an app you can count on...
Basic but helpful — Does what it says it will. Carry your MTA maps on your phone. No frills to this app, but it does work offline so you can access the maps while on the train.