Standard Screwdriver
Long slender screwdriver with standard handle.
I needed a set of small screwdrivers for my bicyle repair toolkit. I wanted maximium versitility in the smallest space. Stores sell combo bits and bit drivers, but most have huge handles and won't fit in my toolkit.
3D printer to the rescue! I designed a medium sized slender handle and printed it up. It works great. The design borrows heavily from this blender tutorial, with some changes and enhancements: http://pages.uoregon.edu/art3d/driver/driver25.html