LaTeX and git. Granted, we're a small company with five people in the tech department, all working the terminal most of the time, so we can choose pretty freely. We're a B2B company. Having solid, continuously improved, and useful documentation to put on the table at the first meeting is a huge win in trust and efficiency.

In my experience, the critical success factor is having someone in the team that truly cares about it. In our case, we had a guy whose peace of mind depended on having everything in order, including well-structured, complete, and correct documentation. He left us a couple of months ago, and already the documentation is starting to deteriorate.