The best interview I’ve had in my career to date is the one for the role I didn’t get. It stuck with me, however, for a couple reasons (both personal and historical). It was an interview for a role with Microsoft in the early 2000s.
The Personal Angle:
As a GNU/Linux user since the early 1990s I had worked in many development environments up to the interview, but always figured out how to make some version of 'NIX my main workstation and toolset. The interview was set up by a contractor I was working with who knew the Microsoft manager and thought I would be a good fit. Up to that time I was very anti-Microsoft but only from the technical aspect. I had yet to work on MS products that worked as well as my 'NIX tools. All I had for the interview was that knowledge-set and perspective, so I was very nervous.
The interviewer was unlike any I’d encountered up to then. He had no script, no prepared questions of any sort. Instead he started the conversation as if we were two geeks at a conference talking about random tech topics. Looking back, I realized he was slowly building up to the more technical questions but wanted to get a sense for how I fit into the tech world. We discussed everything from release management and quality assurance to repository administration and version control. And, surprisingly, we discussed GNU/Linux and the Free and Open Source ecosystems in great detail.
I didn’t get the role but that interview stuck with me. In fact, because of it, I wound up changing a few professional practices and habits that made me a better asset to the company I was working for at the time. It gave me a peek into Microsoft as a community I’d never had and I gained more appreciation for MS because of the conversation. I may never be in the position of giving an interview, but if I ever do it’s his example I’m following.
The Historical Angle:
About three years after than interview, MS went on to surprise the tech community with VS Code and WSL (both of which I now use). Another year or two later they joined the Linux Foundation. I still wonder had my interview been just a couple more years out if I might have gotten the role, but either way I’m happy with the experience.