I occasionally want to leave a screwdriver permanently in a location for adjusting something. This takes the little screwdriver bits that come in the really cheap kits.
I just wanted something that I could whip up in 10 minutes and print in 5.
Requires the knurled surface library at http://www.thingiverse.com/thing:9095
With the parameters set as they are, for me the screwdriver bits fit snugly and securely. If tight or loose for you, just scale appropriately, or use the SCAD to modify.