I think Harajuku and Akihabara (in Tokyo) are enjoyable.
I don't know so much about Akihabara, but my friend said there are lot of game center(do you know this?) to enjoy games. You can stay there till the midnight, if you want to. And so many kinds of game, robot,computer shops.
I often see people in several Game costume at Harajuku. I think Harajuku is a town for all the young people though there is always crowded.
I often go there with my friend just to walk around. There are so many kind of people wearing various kinds of clothes they like. And several kind of cheap shops.
Is this what you wanted to know?