2. Claw Retractor
Well this one sure is weird, but according to the Mirror UK, about 85-percent of people have a muscle called the palmaris longus, which it describes as a “vestigial muscle running from the elbow to the heel of the hand.”
Apparently in some primates, this particular muscle helps in climbing, while the same muscle in felines (and other predators) it is used to draw back in those dagger-like claws. Apparently if you stretch out your hand in front of you and then make a fist (with your thumb tucked under your forefinger), you can see this muscle along the centre of your wrist.