PCalc is by far the best, and also our favorite calculator app for iOS. It has been around for several years, offers a wonderful set of features and sports a beautifully crafted UI.
A recent update added the ability to select from a set of custom icons, and the one featured above, called ‘Six Colors’, is our favorite one from the set. Here are the other icons available in the app:
The above set of custom icons is available via an optional ‘Tip Jar’.
The app itself is priced at $10, but also has a ‘Lite’ version available for Free on the App Store.