One of Dr. Gero's androids. He was created for the sole purpose of eliminating Goku, to take revenge for destroying the Red Ribbon Army when he was a child. Android 16 doesn't respond to commands unrelated to Goku (at first), and will not take orders from anyone. Unlike the other androids, he is purely machine based, and is stronger than the other two androids. He has a powerful nuclear bomb capable of destroying even Cell in his perfect form, however he doesn't get a chance to use it because he had it taken out while Bulma and her father were repairing him.
Android 16 decides to not go along with his mission to destroy Goku, after realizing Dr. Gero was evil. He decides instead to help the other Z fighters destroy cell. He plays a critical role in the Cell saga, after he is blown to smithereens with only his head in tact, he convinces Mr. Satan (Hercle) to throw his head over by where Gohan and Cell are fighting, and convinces Gohan to unleash his hidden powers, by explaining that violence is OK is long is it is used to protect that which you hold most dear. He dies shortly after when Cell crushes his head, pushing Gohan over the edge, transforming into a Super Saiyan 2.
Android 16: You two made too much noise. You scared the birds away.