The timeless HP-12C, surely the greatest financial calculator of all time.
I attended a design workshop run by the UK Design Council. They are trying to encourage companies to use professional designers to improve their products and marketing instead of trying to compete solely on price. Manufacturers in China and India and other emerging economies have labour and overheads which are about one tenth those here in the UK, so trying to undercut them isn't really an option. We were asked to bring an example of "good design" for discussion. Here's what I brought:
The HP-12C financial calculator. Bought around 1990, the HP-12C had already been around for quite a few years, having been introduced in 1981. This one is still using the original batteries. Probably HP's best-selling calculator and an icon in the financial services industry.
And it is still in production!
Of course over the years the technology has changed and the internal component count will have dropped. The newer processors can do complex iterative financial calculations instantaneously where previously there was a noticeable delay. HP found that users were accustomed to the delay and didn't trust the results from the faster processors in the new updated models. So the HP engineers had to artificially throttle back these calculations to "improve" the user experience.
The buttons have that solid HP "clickiness" and the calculator as a whole feels very solid. It is intentionally quite weighty (thanks to a metal plate inside the case). It uses RPN logic of course.