You know when you're entering a long number in your iPhone's Calculator app and you mistype a digit or two? You don't actually have to hit clear and start over.
Delete individual digits by swiping over the numbers (left or right, it doesn't matter which direction.)
Each swipe will delete another digit until your reach zero. (In which case, you probably should have skipped all that swiping and just hit clear.)
Am I the only person who wonders why Apple didn't just include a backspace button?
Bonus Tip: Need a scientific calculator? Turn your iPhone to landscape mode, making sure orientation lock is off, and watch your calculator's abilities magically expand!