Outside the obvious phone, text, and browser most used apps are calculator, flashlight, and alarm clock.
Yes I lead an exciting life.
Never have done the gps/real time directions thing but have occasionally used the compass.
A test tone/sinewave generator & spl meter app came in handy once in awhile when I was doing speakers, at least for sort of "roughing in", getting close in a test box or finding tuning freq. of an existing box.
Have used whatsapp to text
@adi a couple times as the regular one that comes with the phone would charge him for international calling or something.