new to iOS... what are some must have apps, tips/tricks, etc?

Heh, I bet you're quite tired of posting in these type of threads, but also you know that The Verge's search is a serious mess. Despite being an Apple user for 9 years, this is my first iOS device (iPhone 5S), a gift from my sister. I'm not much of a mobile power user as you can guess, but still I want to know some good apps I could be missing, and some tips with the general usability of the OS.

thanks in advance.