Macuahuitls were used by the ancient Aztecs and surrounding indigenous people in warfare. Essentially a narrow wooden paddle with obsidian blades, they were something in between a sword and a club. Their design was such that, rather than killing opponents, they were designed to maim (since dead opponents weren’t useful as sacrifices).
So the question is, what sort of value does a “mac” serve in terms of self defense? Essentially, they serve the same as most other weapons of antiquity; they make great art pieces and can also double as home defense. As always, this is a “sticky” issue since lethal force can have legal consequences even for well-intentioned people looking to simply defend their home, so this is by no means encouragement to use a macuahuitl on anyone. Like any self defense situation, this is a personal choice.