I recommend having at least one project of your own inspiration and creativity that showcases the best of what you have to offer. Something that is very well thought-through, original, showy, and doesn't appear to be slopped together in a quick and dirty fashion. Something highly technical and custom in design that you can brag and talk about.
The reason why is because it will say a lot about your intelligence, your style of doing things, and will be a testament to the quality of your work.
It also serves as a safety-net to protect yourself from having your hard-earned clients from being stolen by the competition. Thats a lesson I learned the hard way. I was once approached by a technology-solutions business stating that they had need of another developer, and they were offering a very attractive hourly rate. They wanted to know my usual rates and wanted to see examples of my work. Foolishly, I gave them both over thinking I had scored a new client. But to my dismay, they then turned around and solicited their services to my client base at a reduced rate lower than my own. I was furious and embarrassed to have been suckered by a false interviewing process, and going after them legally just wasn't an endeavor worth going to the trouble of doing. But today when asked to provide my portfolio, I offer to show interested parties my own projects (I have a few). That keeps me safe from giving customers to masquerading competitors, and it satisfies the authentic ones who rightfully deserve to see the quality of my work before making a hiring decision.