Sharp EL-W516B Scientific Calculator
First we'll warn you that if you don't like a lot of features, this model is not for you. With the EL-W516B, Sharp has reinvented the concept of the scientific calculator. It displays four lines of text and shows entered expressions in condensed textbook form. It sports over 530 scientific programs and four programmable macro keys. You can even solve algebraic equations. The EL-W516B is battery-powered. At lower than $20 why bother with anything else?