I think "θάνατος" is the prettiest word I've ever heard.
edit: I think it's whimsical and interesting that "death" is masculine and "life" is feminine.
Θάνατος is masculine because in ancient times Θάνατος was a deity (and actually a pretty one, no scythes or bones!) and he was a man. Could a woman be a life-taker for the ancient people? No, women were giving life, making kids. :)
Thanatos. Thanatos, in ancient Greek religion and mythology, the personification of death. Thanatos was the son of Nyx, the goddess of night, and the brother of Hypnos, the god of sleep. He appeared to humans to carry them off to the underworld when the time allotted to them by the Fates had expired (britannica)