I think it would be really cool to have a tail that could grab onto things (a prehensile tail). Unfortunately, humans and our closest relatives (the apes) don't. We do have what's called a "vestigial" tail, meaning that it's a sort of evolutionary leftover. It's visible in embryos, but by the time we're born, we just have a few small bones that can't be seen from the outside. Most people don't even know they have tailbones unless they break one. Occasionally, a baby will be born with a tail, but it is usually removed surgically.