A function within calculated metrics which gives the ability to use the number of a specific item. See mocked-up screenshots below for example. As far as I can tell this doesn't exist now? Correct me if I am wrong.
Practical uses (I can think of so many company-specific uses but they will be meaningless so here are a few generic ones)
1) Unique Visitors / Counted months
2) Show number of countries visiting each page
Revenue per Country
3) Show volume of different pages viewed each day to spot trends