Everybody's favorite lit-up phallic symbols! They are sure to inspire sexy-time fics, y/y?
Or perhaps you'd rather take the prompt more literally and write about a visit to a lighthouse. Or maybe a fic about a lighthouse keeper? I can see your hero now, lighting the wick and leaning out over the gallery railing, singing "Candle on the Water"
like Helen Reddy in Pete's Dragon.
More information about National Lighthouse Day here
.Headers light the way to awesome fics!