There is a power to live music that translates well to a radio format. Play a tune on a ukulele or harmonica; surfing listeners will probably pause to see what you're about.
Research an obscure anniversary, discuss it on the air (on or about the date) and play an appropriate setlist. For example, Alexander Hamilton was shot by Aaron Burr on July 11. Songs that fit the theme include "Bang Bang," "Happiness is a Warm Gun" and "There Goes my Gun."
Ask a trivia question with a difficult answer. It doesn't really matter what the prize is; people will phone in the answer if they know it. Come up with a question that people can't easily look up, like "When the Transformers traveled to Earth, which Decepticon stayed on Cybertron?"
Ask your favorite local musician or performance artist to stop by your show for a chat or a song. He'll probably enjoy the free publicity.
Why should artists get all the fun? Ask the most interesting person you know for an interview and talk to her about her job or the funniest or most interesting things that have ever happened to her.