I made a chocolate marshmallow cake roll, which was pretty tasty. I rolled the sections in different thicknesses, so it looked like his retractable light saber toy. I was pretty happy with it. At least everyone could tell what it was, and my son really liked it, so that's really all that matters.
I've used this site before to find fun birthday cake ideas. There are tons of cakes and usually there are at least basic instructions to help you out. If you're looking for cake inspiration, I highly recommend it!