Eyes
A vestigial organ is an organ that has no beneficial use to an organism. Ex. Tail bone in Humans
The largest organ of a human is skin.
The male organ of copulation in humans is the penis.
The answer to that is skin.
Plants,Animals and humans
organ
Skin
Compared to what? It is the only respiratory organ in humans.
In humans the appendix is a vestigal organ and has no function that we are currently aware of.
It depends on the organ, animal species, and disease, but generally, with the diseased organ.
nose!
hearing