From Quora, here are some cool hidden features on your iPhone / iPad:
- Offline google maps by searching "ok maps"
- Swipe in the calculator display to delete a digit
- Turn on field test mode to show signal information by dialing *3001#12345#*
- Double tap a word to select, quadruple tap to select a paragraph, hold one finger at the beginning of text then place another finger at the end to select, double tap but hold and drag second tap to select more text
- Use Guided Access (in settings) to disable buttons or parts of the screen
- Make the camera flash like the Blackberry LED: Setting -> General -> Accessibility -> LED Flash for Alerts -> ON
- Kill many apps at once by swiping up on multiple apps
- After selecting a word, tap Define to get the definition
- Add textexpander style shortcuts, i.e. to insert a specific bit of text, like your email address, type just a few characters. I have mine set to "@@" - Settings > General > Keyboard > Shortcuts section
More here: