Sharanga is the celestial bow of the Hindu God Lord Vishnu. Other weapons of Vishnu include the Sudarshana Chakra, the Narayanastra, the Vaishnavastra, the Kaumodaki mace, Nandaka sword. In South India, (Telangana, Andhra Pradesh, Tamil Nadu, Kerala) Sharanga is also called as Kodanda. In poems written by Ramadasa, the poet used words like Kodandapani to refer to Lord Rama. Even Mirabai referred to Lord Krishna as Kodandadhari.
This bow was crafted by Viswakarma, the Cosmic architect and maker of weapons, along with the Pinaka, the bow of Lord Shiva. Once, Brahma wanted to know who was a better archer, Vishnu or Shiva. Brahma created a quarrel between the two, which led to a terrible duel. The impact of their fight was such that the balance of the entire universe was disturbed. But soon Vishnu was able to paralyze Shiva with his arrows. All the Devas led by Brahma himself begged them to stop, declaring Vishnu the winner as he was able to stun Shiva. Enraged, Shiva gave his Pinaka bow to a king, who was an ancestor of King Janaka, the father of Sita. Vishnu too decided to do the same, and gave his bow to the Sage Richika. In time, Sharanga came into the possession of Parashurama, the sixth avatar of Lord Vishnu and Richika's grandson.
Lord Rama is 7th incarnation of Lord Vishnu. During Sita's Swayamvar, Lord Rama lifts the Pinaka - the divine bow of Lord Shiva as per the contest conditions. Lord Rama tried to tie the string of Pinaka and use it but in the process broke it. Sage Parashurama comes to the place once he notices the same. Parashurama challenges Lord Rama to hold Sharanga if he could. Lord Rama lifts it easily. In some versions, it is also said that Parashurama loses his power, obtained as incarnation of Lord Vishnu, to Lord Rama as he hands over Sharanga to Lord Rama. It is also said that Lord Rama appeared as Lord Vishnu for Parashurama after holding Sharanga. Parashurama immediately blessed Lord Rama and suggested him to use Sharanga as his bow throughout his life. Lord Rama politely obeyed Parashurama's words. Lord Rama fought many battles with this celestial and divine bow only. The fierce Rama-Ravana battle was also fought with Lord Rama having Sharanga. Lord Rama killed many mighty warriors like Ravana, Kumbhakarna using this Sharanga. At the time of Ascension; Lord Rama gave this to God Varuna, the lord of the hydrosphere.
Lord Krishna is 8th incarnation of Lord Vishnu. Lord Agni (God of fire) suffered from a digestive problem because of intake of lot of ghee from the yagnas performed by many people. He approached Lord Brahma for help. Lord Brahma told him to burn entire forest of Khandava to clear the problem and satisfy hunger. Soon Lord Agni came to know that Takshaka, the serpent-king lived in the same forest and was a friend of Indra's. Indra also promised that he would be on Takshaka side to save the forest. Once when roaming in the Khandava Vana, Arjuna and Krishna met Agni. Agni explained the situation and Lord Krishna promised Agni that he and Arjuna would be on Agni's side. Arjuna told Agni that he and Lord Krishna need some celestial bows and weapons to fight with divine warriors like Lord Indra. Agni told them that he could present weapons with help of Varuna. Then Arjuna obtained celestial bow Gandiva and Akshaya thruthiya. And Lord Krishna got Sudarshana Chakra and Sharanga during the Khandava-dahana. In this war Lord Krishna fought with rest of the gods and Arjuna fought with Lord Indra. Lord Krishna and Arjuna won the war. From that moment Lord Krishna used this Sharanga as his bow. In Krishna-Arjuna war also Lord Krishna used Sharanga. That's the reason why neither Lord Krishna nor Arjuna gained the upper hand in the war. Just before his ascension, Lord Krishna returned it to Varuna by throwing it back into the ocean, Varuna's domain. Sharanga also appears during a duel between Lord Krishna, the eighth incarnation of Lord Vishnu, and Shalva, the demon of mystical powers. Shalva strikes Krishna's left arm causing him to drop Sharanga. Later, Krishna severs Shalva's head with Sudarshana Chakra.