Nandaka

In Sri Vaishnavism (a major Vaishnava tradition), the saints Annamacharya and Peyalvar are considered to be the avatars of Nandaka.

Vishnu blessed the asura that his fallen body-parts will be employed for the manufacture of weapons on earth.

[2] Vishnu is usually depicted as four-armed with the four attributes in his hands: the shankha (conch), the Sudarshana Chakra, the padma (lotus) and the Kaumodaki gada (mace).

[3] The Harivamsa as well as the Brihatbrahma Samhita prescribe that the sword be shown in Vishnu's four-armed images.

[4] Vishnu's avatar Vamana is described to hold the Nandaka in his right hand in the Kalika Purana.

It says that the 'Great God' (Maheshvara, an epithet of Shiva) takes the form of a flaming sword of knowledge, one that destroys ignorance.