Inspired by Adam Savage's holster, made out of aluminum for his Leatherman Wave (you can see the video here). Prints in one solid piece, and it's parametric to work for any multitool you could want to store and access with one finger; included STL is for the Leatherman Wave.
This thing is solid and works great.

Printed at 0.2mm layer height with 20% infill and 2 shells at 235ºC on a Makerbot Replicator 2. No rafts or support material needed.