Absolutely love HP calculators. Almost fourty years ago, my HP28s introduced me into programming in RPL, a stack based Forth like language combined with elements from Scheme (Lisp), and symbolic calculation. It was a language that was way ahead of its time, nothing I had seen in Pascal or C. Only a few years later in Mathematica. From there I learned Scheme, and was introduced to the book SICP. All of this had a lasting effect on how I program and think.

HP started my journey so to speak :)

I also had one of those mentioned in the article, just for nostalgia. Rock solid, RPN based, lovely product. The kind of product companies do not build anymore (products that will last you a lifetime)