Google maps. I live in Japan and I don't read Japanese so it's extremelly helpful. Even when I was living in London 2 years ago, I was quite upset during the two months Google maps was not on iOS.
Even though I don't FB a lot, the App is quite handy to message someone that's not as tech savvy (or don't have a smartphone), especially in groups, and keep track of the convo history.
Ola cabs / Uber for India - I dont own a car so these apps were pretty much indispensable for me, but now they have been banned pretty much in many Indian cities.
