Hey Mensa,
1) Your fingernail has no cells. It is keratin, like your hair or a horse's hoof and is just protein.
2) It is a unique, alive human being.
In the past I have listed things that an organism must do to be living. This was out of the first chapter of my basic biology book from college. (Look it up if it wasn't erased by the last big crash- I don't want to go through it all again.)The fertilized egg meets each of these criteria. The fertilized egg has a unique set of genes, unlike any other person before or after it (except for identical twins, which are actually clones). Even identical twins have slight differences due to differential gene expression due to slightly different environments in utero.