I'm using a HP48G. [0]
It's just a joy to use and i also like it a lot design wise.
I like that it has a big display for 4 RPN rows, but i admit that that's something software calculators would even be better at.
It definitely has a nostalgic/romantic side to it for me.
Oh and for every day stuff, i really like to use Spotlight on macOS. It's really convenient: Command+Space, then just type the expression into the search box.