The CAS software on HP calculators is amazingly useful, especially considering the limitations of the hardware it's running on.

Dwm and dmenu. Top notch polish, true minimalism

Robinhood is probably the best software I regularly use. It's extremely smooth and intuitive for how powerful it is now. The way they present and explain options and allow you to enter complex multi-leg option trades on mobile is super impressive. On top of that it just works really well (these days).

I don't know if its polished in the traditional sense, but yt-dlp feels so perfect for what it was designed to do.

I don’t think there is any particularly perfect software

Monarch Money is incredibly smooth and functional considering the complexity. Maybe it benefits from the comparison with the mess that was Mint though, haha.

Ghostty is exceptionally good at what it was made for

For me, i think it’s notion, it’s well thought.

BBEdit.

NetBSD on plain console.

I find 1Password to be very smooth and intuitive to use (ignoring its sometimes unfortunate iOS integration, which is Apple’s fault).