The one they seek.
Every shop has one — that chain tool that trumps all chain tools. The one the mechanics seek out when they're working on their best customers' bikes; it's precise, well-weighted, and smooth. If you need one of your own, then spring for the Unior Screw Type Chain Tool, compatible will all modern drivetrains, including but certainly not limited to 11-speed systems from SRAM, Shimano, and Campagnolo.
setting chain pins