I love this thread. Several interesting knives I've never heard of.

For the last six or seven years my favorite has been this safety orange Techni-Edge Swift Switch. It has my preferred bent handle and a more solid blade purchase than most of the non-retracting knives I've had. The black spring-loaded block pivots off the back allowing the two halves to separate for tool-less swift blade switches. There's space for ten extra blades, and the blade retainer is held in place by a magnet so it doesn't fall out during swift switching. The magnet also snicks the new blade in place until the two halves can be swiftly reassembled.

These were on display at the board store and came with the same plastic sheath Occidental now includes for sharps with their toolbelts. initially, the sheath caught my eye more than the knife. But after a week of use, and intuiting that like so many good ideas it was doomed to be discontinued, I went back and got another for a spare. Pictured is the first one. 

In 2018 Stanley bought Techni-Edge and from the look of things, drowned them in the bathtub. They were too swift to live.