Linux

There's an old joke from a couple of decades ago about what operating systems would be like if they were airlines:

Linux Airlines

Disgruntled employees of all the other OS airlines decide to start their own airline. They build the planes, ticket counters, and pave the runways themselves. They charge a small fee to cover the cost of printing the ticket, but you can also download and print the ticket yourself. When you board the plane, you are given a seat, four bolts, a wrench and a copy of the seat-HOWTO.html. Once settled, the fully adjustable seat is very comfortable, the plane leaves and arrives on time without a single problem, the in-flight meal is wonderful. You try to tell customers of the other airlines about the great trip, but all they can say is, “You had to do what with the seat?”

Gentoo is still very much a "You had to do what with the seat?" distro, while most others have retired that concept to varying degrees, at the cost of the seats being less easy to perform unusual adjustments on.