As a software engineer I frequently encounter things that make me say, "Nice! I can tell a lot of work went in to that." Or other times, "what a clever use of that technique!" But on occasion there is something that just works like magic and I am left with no clue how that was even possible.

For me this includes
- exwm
- git diff
- email
- web sockets

How about you? What is some Magic Tech software in your book?