David (Israelite king)
David was the second king of Israel, under whom the country flourished and, according to the first chapter of Matthew, an ancestor of Joseph. Jesus Christ is considered to be a member of the "house of David" (Luke 1:27, KJV) because he was born to Joseph's wife Mary. David was a righteous king, so much so that even when his successors committed egregious sins, God kept faith with them for David's sake (see, for example, 1 Kings 11:34). He was also a poet and musician, and is credited with having written many of the Psalms.
David is famous for his battle with Goliath, a giant of a man in the Philistine army which was at war with Saul, the then king of Israel. Goliath had offered to take on anyone from the Israelite army, with the outcome of the battle to be decided by this one-on-one fight. But nobody on the Israelite side was prepared to take him on. David, visiting his brothers in the Israelite army and puzzled why nobody was willing to accept Goliath's challenge, decided to take Goliath on himself. Trusting God to help him win, and using skills developed in warding off animals attacking his father's sheep, David confronted Goliath on the Valley of Elah. Goliath, having challenged the Israelite army daily for nearly six week, was insulted that it was a boy who came to meet him. But David, proclaiming that he was coming in the name of the almighty Yahweh, used his slingshot to hit Goliath with a stone on the forehead, knocking him unconscious. He then used Goliath's own sword to kill and then behead him.