The Casio fx-992s is, without a doubt, my favourite calculator.
I’ve had my fx-992s since I did my GCSEs and it’s served me very well. I own three – the original (shown on the left), the backup (shown on the right) and the backup-backup (not shown). I try to avoid having all three in the same place in case of catastrophic calculator loss.
I like the fx-992s because it doesn’t have any of the fancy, difficult to use “functions” that I see in my pupils’ calculators: it doesn’t do surds, it doesn’t give every answer as a fraction or require you to use Natural Textbook Display and it doesn’t have a weird cursor-controller joysticky thing.
Most of the pupils I teach can’t use their calculator properly – the calculator companies’ efforts to make calculators easy to use have done exactly the opposite.