[niftich]

Midnight Commander and its spiritual predecessors going all the way back to Norton Commander and Volkov Commander are marvellous examples of TUI.

They're intuitive, interactive, come with embedded help, and use text mode to present a sophisticated, productive interface.

[vram22]

The Norton Editor (NE) was very good too. Really fast. Probably written in assembly, maybe by Peter Norton himself. I had bought and read a book of his on programming in assembly language (x86) for the IBM PC. Also very good. He developed a TUI hex editor in the book as a running case study, IIRC.

Also the Norton Guides were fantastic. TSRs [1], but with a TUI. You could get guides for C, dBASE, Clipper, Assembly, etc. I loved the TSR popup experience on DOS.

[1] Terminate and Stay Resident programs. They hooked into a keyboard interrupt to allow them to pop on a press of a hotkey.