In Osaka i really liked Sinsekai.
It might be boring for some people but it certainly is a totally different side of Japan.
Start walking from the closed down shopping center / Amusement Park (Festival Land) towards Sinsekai (maybe someone can give a more exact route) and you can see old places filled with old people playing go, old arcades with cheap games,... Than you come to the sign of the "new world" wich is now just a run down amusement part of town. Check out old style pachinko where you actually get to shoot every single ball (a big one) by hand, win some chocolate, get some cheap lunch and leave this strange place again.
My blog with a few pic to that area.