Park CT-5 Chain Tool
Our go to in the workshop even though we have full size chain tools that cost 3x as much.
More expensive chain tools were designed to be better at fastening a chain together so that it was less likely to break in use.
This is unnecessary now that chains have a quick link.
Today, the only purpose of a chain tool to shorten a chain, so really is no need to buy a $30 to $50 premium chain tool.
Small enough to take along on multi-day trips.
Compatible with 5 to 12 speed chains from Shimano, KMC and Sram.