For me, it would be spinach salad. It sounds good, and is good for you, but I find it very overrated.
BTW, I like Okonomiyaki. When I first started going to Osaka, I thought I would find it in every restaurant - kind of like eggs in the US. It turned out to be not quite as common as a thought but I found and ordered it in a real 'dump' of a place outside of Osaka Station. It was good and I have been eating it ever since.