Perhaps the question instead should be "What do I have to offer an agent?" So many artists are seeking an agent as if an agent is going to make their dreams happen for them.
Unfortunately, that's not really an agent's job (at least, not really anymore.) An agent is in it for the money. As they should be. It's a business, and you are a product. And there's nothing wrong with that. Build your resume, your portfolio, and your visibility as a product that's worth real money. If you're a writer, make your movie. If you're an actor, do a showcase (or make your own movie!) Don't just write a script and try to get an agent with a stack of 120 sheets of paper (I mean, you can totally try that, but don't get your hopes up.) Make your career- then your agent will help you sell it.