Fun fact: Apple's internal bug tracking tool, Radar, traces its origins to a pen-and-paper tracking system from the very early days.

In a similar fashion to RAID from the article, it's use expanded way beyond the original use case and is now used by nearly every team at Apple, from hardware, to test, to marketing, retail, and everything in between.

It's often the butt of a lot of jokes as most people hate its dated and confusing UI :).

edit: Though to be fair, the team maintaining it has made massive strides recently to completely revamp the UX which is no small feat given such a wide range of business critical use cases.