Park Tool PH-1 Hex Wrench Set
My top pick for hex key wrench sets is actually a set that is made for bicycle maintenance. This is a most unique set in that five of the wrenches have built-in spinners, which the manufacturer calls speed bearings for quick removal of long hex screws. It might be easier to think of it as a short sleeve over the long shaft of the wrench. Once the screw is broken loose, you can hold the sleeve with one hand, while spinning the handle of the wrench with a finger of the other hand (similar to spinning a star wrench used for wheel lug nuts). All the wrenches have ball ends on the long shaft, and chamfered ends on the short shaft. The handles are probably the most comfortable on the market as they are well fitted to the hand while a wall-hanging holder keeps your tools organized.