If you saw my Hiroshima Food section you have been introduced to okanomiyaki. Osaka Okanomiyaki is a similar but it does not have noodles. Also the ingredients are mixed up instead of layered. It's quite good, and if you're there you should try it. That said I prefer Hiroshima style okanomiyaki.
Oshi-zushi is an Osaka style of sushi. I didn't get any but I think it's worth mentioning because it's a well known Osaka food. Oshi-zushi is a style of sushi using cooked fish and seasoning pressed into wooden boxes making little rectangles. I found a link teaching you how to make your own Oshi-zushi.
Here's a video I found of some Osaka foods:
Here's random pictures of some of the foods I ate:
I got this for about $6 at a local market. I went late at night so everything was marked down. I was quite pleased. Cheap living in Japan.