iOS ships with a handful of generic utility apps such as Calculator, Stocks, Weather and Voices Memos to name a few. These are not the only apps that come pre-installed; but they usually fall under scrutiny from a number of posts recommending that you quickly tuck them in a folder, and replace them with any number of apps from the App Store.
One app that I realized that is not on iOS is a Dictionary app. You can select a word; click Define and a style sheet displaying the definition appears. However there is not a full blown Dictionary app such as the one that ships with Mac OS X that you can search. Another feature of the OS X dictionary is that it has a built in Thesaurus.
I know that a dictionary app isn't going to change the world or anything, but it is interesting to me to see what Apple choses to add or not add to iOS. With that said I am trying real hard to not launch into a long drawn out post about the fact that the iPad doesn't ship with the Calculator, or Voice Memos apps.