A nut driver for a small cordless screwdriver.
Being made of plastic has the added advantage of acting as a clutch (when the plastic slips and squishes at high torques). I use it to loosely secure hose clamps and it has surprisingly met my needs quite well because there is a built in clutch (the plastic part slips loose a bit).
It is way easier to use this nut driver than a slotted screwdriver because the slot slipped out too often.

Made out of ABS on a Thingomatic with 100% infill.
You can alter the scad file to suit your needs ... especially the fit in the screwdriver which may be too loose for some applications.