I guess my definition of elegant would be software that has fantastic UX and just works and works so well it boggles my mind how well it works. I'd also extended that to include a foundational core that all other parts can be built off of. In that case, I'd go with vim. I'm not even a huge Vim guy (use it for notes and remote stuff, but not my primary editor), but the concepts are simple and oh so powerful. It's just building blocks on top of text editing.
Pipes in Unix as a concept are also a great abstraction. A bit dated, but still every powerful today.
Files in Unix as well. Some people have gripes which are fair, but the idea that a device, a file, and a socket are all accessed via the same API is fantastic. Of course there are issues, but it's generally worked really well for me.
Yes!! Learning Vim was a revolution for me. It eliminated the strain and repetitive movement of constantly turning to the mouse or arrow keys to navigate the cursor around. Just learning how to jump between INSERT and VISUAL mode and move the cursor was enough to hook me. Now I use nvim + COC for Intellisense-style completion and it's a joy. I love using this software!
Pipes in Unix as a concept are also a great abstraction. A bit dated, but still every powerful today.
Files in Unix as well. Some people have gripes which are fair, but the idea that a device, a file, and a socket are all accessed via the same API is fantastic. Of course there are issues, but it's generally worked really well for me.