Raksha Bandhan

Several. Indrani tied a thread on Indra's wrist before battle with the asuras. Draupadi tore her sari to bind Krishna's bleeding finger, and he pledged to protect her. Yama's sister Yamuna tied a thread and he granted her immortality.

A sister ties a rakhi on her brother's wrist, applies tilak, and he gives a gift and a promise of protection. Now widely extended beyond siblings, to cousins, friends, soldiers.

Sweets, ghevar in Rajasthan, coconut sweets on the coast, kaju katli and barfi generally.

The same tithi carries entirely different observances elsewhere. In Maharashtra's coastal districts it is Narali Purnima, when coconuts are offered to the sea and the fishing season opens. In the south it is Avani Avittam / Upakarma, when the sacred thread is changed. In Odisha it's Gamha Purnima. So one full moon holds four unrelated festivals.