Maybe a pot of gold is too much to expect, but a beachful of golden sand is a sure thing on Kauai's several-mile run of coast from Haena Beach Park and around Kepuhi Point to Charo's Beach. During the winters, normally in the afternoons with a few clouds in the sky, seeing a rainbow is a near certainty.
High surf is also fairly common. Stay well back of these big boys—away from sloping wet sand. Always keep an eye on waves if you're walking anywhere near the foam line.
Kiteboarders like the wind inside the reef at Charo's (named for the oddball TV star from the 70s who had a restaurant here, today the site of Hanalei Colony Resort). Currents here are normally treacherous during the winter.
Rainbow hunters are often joined by sea shell seekers, who harvest tiny 'Ni'ihau' shells along the high-water line. There are many places to park along this stretch of coastline, which includes Tunnels, the popular snorkeling beach. Kauai Trailblazer has specific directions to several shoreline access spots where you won't find crowds.