I am looking for a word that describes/means the appendices at the ends of limbs (namely hands and feet), meaning a singular one of them.
Bonus: a word that describes/means all of them
For the plural, consider extremities. Its singular is extremity.
From en.wiktionary, extremity has a sense (among others) of “A hand or foot”.
(It also has a sense of “A limb”, ie an arm or leg, so may be imperfect for your needs.)
As noted in tunny's comment, collinsdictionary.com shows similar definitions, for extremities and extremity respectively, with emphasis added:
• (formal) hands and feet
• a limb, such as a leg, arm, or wing, or the part of such a limb farthest from the trunk
The terms appendage and appendages are relevant too, although rather less specific to hands and feet than are extremity and extremities. From en.wiktionary, appendage means “an external body part that projects from the body”. Most humans have five main appendages, ie head, arms, legs. Typical human males have another appendage, or member, sense 4. I don't know if breasts count as appendages. If we count fingers and toes as minor appendages, I suppose noses and ears should count as well.