We’ve been having a good old time with this over on the Pocket Knife community, but I figure there’s probably a lot of crossover with this crowd as well.
I’m sure you’ve seen various clever little one piece utility knife blade holders on Thingiverse and so forth, and while they’re quite functional I don’t think they’re nearly as overwrought or silly enough, nor require quite enough components.
Rather than repeat my entire post from there over here, I’ll leave you with these:
Link to .STL Files And Assembly Instructions
It rides in a track that encloses the top and bottom edges by a couple of mm.
The rear has an end stop, also. It can’t fly in any direction, and the only way it’s going any time soon is out the front if you press down the flexture that has the locking pins on it.