Having lived a life based upon self reliance as much as I could in terms of building and repairing all sorts, I have gathered tools a plenty which were highly valued.
Over the last few years I have given most of my kit away to a young neighbour who is ever working on something in his yard.
Least used, I suspect my imperial micrometre which was used for setting valve clearances on the various TC Lotus and Jaguar cars I owned over the years...