One++ is the flagship killer calculator app of Android
In addition to all that mathematical goodness (or nightmare, make of it what your math skills allow), One++ is a total looker. The interface is inspired by Samsung's later-day TouchWiz menu and its obsession with flat circles laying on a flat background, which means you are in for quite a bit of scrolling up an down, in exchange of having to use what's arguably the most dated interface paradigm of all time - that of the pocket calc. Moreover, One++ freshens things up with 10 scroll animations, four material themes (dark, light, black & translucent), and 5 interface designs to choose from.
If One++ sounds like something that may be of use to you, the app is just one download away, and there are no invites required.