I've only ever seen master link pliers in one person's (massive) toolbox, Guy Martin's. They were Snap-On, but Motion Pro make them too. If you don't know what they're for, the idea is they have ever so asymmetrical jaws, so it's easier to push the split link off. I take chains off all the time, so after years of planning to, I finally chopped up a pair of worn out pliers that I can't even remember acquiring. Hey presto, homemade master link pliers.
1-minute in the vice