If you were a big fan of programmable calculators in University (or highschool, I guess it depends on how much $$ you were willing to spend on a calculator back then) then you should like this;
C# Programmable Calculator is a Reverse Polish Notation (RPN) calculator with custom buttons programmable in C#.
There is a shareware version available for download or you can register to get additional features...

[Listening to: One Week - Barenaked Ladies - Disc One: All Their Greatest Hits (1991-2001) (02:49)]