Shibuya has the famous crossing. Like everywhere, there are gadgetry shops, but it is really more the place for serious, but cheap, fashion shopping. You want a t-shirt with some baffling claim, there are whole mini-malls full of them. Socks with teeth? What colour you want, lady?
Make triumph noise and crap your hands!!
My favourite Starbucks, though. Grab a table overlooking the crossing, and enjoy the show, with some weird coffee concotion.