At A-level we all bought the (at the time) new graphical scientific Casio calculators (good for cheating in exams), which allowed for graphical graphs to be plotted, as well as being able to program them, and mine is still working perfectly. And I've only ever had to replace the batteries once.

The one I got looks quite cool too with a flip open case and touch buttons, which is quite unusual for a calculator.

It is this FX-7500G one:



Although I tend to use a most standard Sharp one I have for most things.

How sad, we are now discussing calculators!