HP12C

I have been using various models of HP Calculators for years. They are by far, the best financial and general purpose calculators available on the planet - the best feature being RPN.
Once you have used and mastered RPN you will not ever want to go back to basic methods.
Accolades and a HUGE thank you to HP for this App. Finally, we have a superb calculator for the iPad and one that works brilliantly.
Worth ever penny and has my highest recommendation.

DavTinDan about HP 12C Financial Calculator, v2.0.1