Chaitanya Mahaprabhu (1486-1534)
Lord Chaitanya is considered to be an avatar of Krishna and Radha, imbibing both their qualities. He is often referred to as a "rasik" saint, which is another way of saying that he considered love towards the divine as the supreme path. The way that one develops supreme love towards the lord is through the chanting of his divine name. He advocated the use of the Hare Krishna Mahamantra as the path to develop absolute love for Krishna.
He also is the composer of the beautiful "Siksatakam".