Sharp ZQ-5000

Much more than a calculator, this was an early PDA. In fact, the term "PDA" didn't yet exist and it was called a "electronic organizer". Before this, you carried everything around in a little looseleaf notebook that didn't stay little for long. This fit neatly in the inside breast pocket of a suit jacket. Solidly built with just the right heft, it closed with a positive lock and was well protected in its hard but slightly rubbery shell.