Milwaukee Off-Set Power Screwdriver Head
Offset drill adapter
I have used my offset screwdriver head ($26) for around 15 years and it enables me to get to screws in tight places where you might otherwise only be able to use a stubby screwdriver.
I find that the torque transfer is excellent, although sometimes the extra grip does come off. I have used it in my cordless drill as well as handheld, and it is designed for any combination of bits to be fitted. It does require the use of both hands but this means that one hand is being used to steady or apply downward force to a screw while the other imparts the turning force.05/31/19
(This is a Cool Tools Favorite from 2011 — editors)