Kovilpatti's main claim on the Tamil culinary map is kadalai mittai — peanut brittle made with jaggery rather than refined sugar. Stalls clustered around the bus stand and along the main bazaar street sell it by weight, in glossy slabs that snap into shards.
The local style is denser and less sweet than the kadalai you get elsewhere in Tamil Nadu, and the better-known makers have been at it for generations. Buy a packet for the road or as a gift; it keeps for weeks in the wrapping. Ask for "Kovilpatti kadalai mittai" by name elsewhere in the state and people will know exactly what you mean.