App: RPN Big Float Calculator
Developer: Stephan Jancar
Genres: Bildung, Produktivität

Perhaps the most accurate calculator on the iPhone.

Precision from 16-bit up to 100.000.
Fast Calculation in RPN-Mode or direct formula input.

Lots of functions up to elliptic integrals, theta-functions, gamma and log gamma. 
Built in constants for gamma, pi, Feigenbaum.
Calculation mode for complex numbers, quaternions, integers and p-adic numbers.
Nerdy functions with Klingon user-Interface.

Release notes:
Representation of numbers in different number systems (Egyptian, Roman, Tibetan, ...)