I consider HP-28S a work of art. The programming language can be described as an effective mixture of Forth, Lisp and even APL and J. The memory was also very efficiently used, the HP-28S had whole 32K! (not a little for that time).
And all that with 4-bit CPU (!) which worked for a very long time on very small batteries.
And all that with 4-bit CPU (!) which worked for a very long time on very small batteries.
https://en.wikipedia.org/wiki/HP-28_series