My favorite app are Viber and Whats app. Most of my small business clients are on those and in order to save cost of calling and messageing we use these applications. You can talk  and text free with these applications.....

HI,

Had a long thought and dn't know if it is an app but I thinking getting my mail on my phone would be number 1 for me. The next would be Google alerts.

Peter

Google Analytics dashboard on my iPhone.

I like Cheap Parking on my iPhone. Finding parking in the city is a nightmare, so the app solves a real problem for me. It's simple to use because it's intuitive and knows what I want - either 'cheapest' or 'closest' (from my destination). It's effective because it's always updated with all the early bird or flat rate specials. And lastly, it finishes the job - by giving me directions on how to get to the parking station of my choice. You can't really ask for more. Now that's what I call a smart app. :)

Evernote app on my Iphone. Access notes and write notes!