White pages & yellow pages are both stored on the phone so you don't need to lug around phone directories. Can be handy for folks that just want to use a phone to talk but don't know number right off hand.
Fairly accurate level.
Decent GPS with navigation.
GasBuddy to check the lowest price of fuel in any area you happen to be in. 
Edit, consult, or save Office documents
Check wind speed, temp, wind direction or other data relayed by the weather station in my yard.
Timer &/or stop watch.  
Dictionary & encyclopedia in your pocket.
Magnifying glass for tired & weak eyes.